{"id":28286,"date":"2022-01-13T18:14:05","date_gmt":"2022-01-13T12:44:05","guid":{"rendered":"https:\/\/infinitylearn.com\/surge\/?p=28286"},"modified":"2022-04-25T15:18:42","modified_gmt":"2022-04-25T09:48:42","slug":"three-dimensional-geometry-class-12-notes-maths-chapter-11","status":"publish","type":"post","link":"https:\/\/infinitylearn.com\/surge\/study-materials\/three-dimensional-geometry\/class-12-notes\/maths-chapter-11\/","title":{"rendered":"Three Dimensional Geometry Class 12 Notes Maths Chapter 11"},"content":{"rendered":"<p><strong>Direction Cosines of a Line:<\/strong> If the directed line OP makes angles \u03b1, \u03b2, and \u03b3 with positive X-axis, Y-axis and Z-axis respectively, then cos \u03b1, cos \u03b2, and cos \u03b3, are called direction cosines of a line. They are denoted by l, m, and n. Therefore, l = cos \u03b1, m = cos \u03b2 and n = cos \u03b3. Also, sum of squares of direction cosines of a line is always 1,<br \/>\ni.e. l<sup>2<\/sup> + m<sup>2<\/sup> + n<sup>2<\/sup> = 1 or cos<sup>2<\/sup> \u03b1 + cos<sup>2<\/sup> \u03b2 + cos <sup>2<\/sup> \u03b3 = 1<br \/>\nNote: Direction cosines of a directed line are unique.<\/p>\n<p><strong>Direction Ratios of a Line:<\/strong> Number proportional to the direction cosines of a line, are called direction ratios of a line.<br \/>\n(i) If a, b and c are direction ratios of a line, then \\(\\frac { l }{ a }\\) = \\(\\frac { m }{ b }\\) = \\(\\frac { n }{ c }\\)<br \/>\n(ii) If a, b and care direction ratios of a line, then its direction cosines are<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71911\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-1.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"452\" height=\"66\" \/><br \/>\n(iii) Direction ratios of a line PQ passing through the points P(x<sub>1<\/sub>, y<sub>1<\/sub>, z<sub>1<\/sub>) and Q(x<sub>2<\/sub>, y<sub>2<\/sub>, z<sub>2<\/sub>) are x<sub>2<\/sub> \u2013 x<sub>1<\/sub>, y<sub>2<\/sub> \u2013 y<sub>1<\/sub> and z<sub>2<\/sub> \u2013 z<sub>1<\/sub> and direction cosines are<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71912\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-2.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"83\" height=\"69\" \/><br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71913\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-3.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"136\" height=\"72\" \/><br \/>\nNote:<br \/>\n(i) Direction ratios of two parallel lines are proportional.<br \/>\n(ii) Direction ratios of a line are not unique.<\/p>\n<p><strong>Straight line:<\/strong> A straight line is a curve, such that all the points on the line segment joining any two points of it lies on it.<\/p>\n<p>Equation of a Line through a Given Point and parallel to a given vector \\(\\vec { b }\\)<br \/>\nVector form \\(\\vec { r } =\\vec { a } +\\lambda \\vec { b }\\)<br \/>\nwhere, \\(\\vec { a }\\) = Position vector of a point through which the line is passing<br \/>\n\\(\\vec { b }\\) = A vector parallel to a given line<\/p>\n<p>Cartesian form<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71914\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-4.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"197\" height=\"56\" \/><br \/>\nwhere, (x<sub>1<\/sub>, y<sub>1<\/sub>, z<sub>1<\/sub>) is the point through which the line is passing through and a, b, c are the direction ratios of the line.<br \/>\nIf l, m, and n are the direction cosines of the line, then the equation of the line is<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71916\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-5.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"193\" height=\"53\" \/><br \/>\nRemember point: Before we use the DR\u2019s of a line, first we have to ensure that coefficients of x, y and z are unity with a positive sign.<\/p>\n<p><strong>Equation of Line Passing through Two Given Points<\/strong><br \/>\n<strong>Vector form:<\/strong> \\(\\vec { r } =\\vec { a } +\\lambda \\left( \\vec { b } -\\vec { a } \\right)\\), \u03bb \u2208 R, where a and b are the position vectors of the points through which the line is passing.<\/p>\n<p><strong>Cartesian form<\/strong><br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71917\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-6.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"223\" height=\"60\" \/><br \/>\nwhere, (x<sub>1<\/sub>, y<sub>1<\/sub>, z<sub>1<\/sub>) and (x<sub>2<\/sub>, y<sub>2<\/sub>, z<sub>2<\/sub>) are the points through which the line is passing.<\/p>\n<p><strong>Angle between Two Lines<\/strong><br \/>\n<strong>Vector form:<\/strong> Angle between the lines \\(\\vec { r } =\\vec { { a }_{ 1 } } +\\lambda \\vec { { b }_{ 1 } }\\) and \\(\\vec { r } =\\vec { { a }_{ 2 } } +\\mu \\vec { { b }_{ 2 } }\\) is given as<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71919\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-7.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"157\" height=\"84\" \/><br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71920\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-8.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"640\" height=\"269\" \/><\/p>\n<p><strong>Condition of Perpendicularity:<\/strong> Two lines are said to be perpendicular, when in vector form \\(\\vec { { b }_{ 1 } } \\cdot \\vec { { b }_{ 2 } } =0\\); in cartesian form a<sub>1<\/sub>a<sub>2<\/sub> + b<sub>1<\/sub>b<sub>2<\/sub> + c<sub>1<\/sub>c<sub>2<\/sub> = 0<br \/>\nor l<sub>1<\/sub>l<sub>2<\/sub> + m<sub>1<\/sub>m<sub>2<\/sub> + n<sub>1<\/sub>n<sub>2<\/sub> = 0 [direction cosine form]\n<p><strong>Condition that Two Lines are Parallel:<\/strong> Two lines are parallel, when in vector form \\(\\vec { { b }_{ 1 } } \\cdot \\vec { { b }_{ 2 } } =\\left| \\vec { { b }_{ 1 } } \\right| \\left| \\vec { { b }_{ 2 } } \\right|\\); in cartesian form \\(\\frac { { a }_{ 1 } }{ { a }_{ 2 } } =\\frac { { b }_{ 1 } }{ { b }_{ 2 } } =\\frac { { c }_{ 1 } }{ { c }_{ 2 } }\\)<br \/>\nor<br \/>\n\\(\\frac { { l }_{ 1 } }{ { l }_{ 2 } } =\\frac { { m }_{ 1 } }{ { m }_{ 2 } } =\\frac { { n }_{ 1 } }{ { n }_{ 2 } }\\)<br \/>\n[direction cosine form]\n<p><strong>Shortest Distance between Two Lines:<\/strong> Two non-parallel and non-intersecting straight lines, are called skew lines.<br \/>\nFor skew lines, the line of the shortest distance will be perpendicular to both the lines.<br \/>\n<strong>Vector form:<\/strong> If the lines are \\(\\vec { r } =\\vec { { a }_{ 1 } } +\\lambda \\vec { { b }_{ 1 } }\\) and \\(\\vec { r } =\\vec { { a }_{ 2 } } +\\lambda \\vec { { b }_{ 2 } }\\). Then, shortest distance<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71922\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-9.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"192\" height=\"82\" \/><br \/>\nwhere \\(\\vec { { a }_{ 2 } }\\), \\(\\vec { { a }_{ 1 } }\\) are position vectors of point through which the line is passing and \\(\\vec { { b }_{ 1 } }\\), \\(\\vec { { b }_{ 2 } }\\) are the vectors in the direction of a line.<\/p>\n<p><strong>Cartesian form:<\/strong> If the lines are<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71923\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-10.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"414\" height=\"59\" \/><br \/>\nThen, shortest distance,<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71924\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-11.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"431\" height=\"139\" \/><\/p>\n<p><strong>Distance between two Parallel Lines:<\/strong> If two lines l<sub>1<\/sub> and l<sub>2<\/sub> are parallel, then they are coplanar. Let the lines be \\(\\vec { r } =\\vec { { a }_{ 1 } } +\\lambda \\vec { b }\\) and \\(\\vec { r } =\\vec { { a }_{ 2 } } +\\mu \\vec { b }\\), then the distance between parallel lines is<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71925\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-12.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"117\" height=\"81\" \/><br \/>\nNote: If two lines are parallel, then they both have same DR\u2019s.<\/p>\n<p><strong>Distance between Two Points:<\/strong> The distance between two points P (x<sub>1<\/sub>, y<sub>1<\/sub>, z<sub>1<\/sub>) and Q (x<sub>2<\/sub>, y<sub>2<\/sub>, z<sub>2<\/sub>) is given by<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71926\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-13.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"365\" height=\"52\" \/><\/p>\n<p><strong>Mid-point of a Line:<\/strong> The mid-point of a line joining points A (x<sub>1<\/sub>, y<sub>1<\/sub>, z<sub>1<\/sub>) and B (x<sub>2<\/sub>, y<sub>2<\/sub>, z<sub>2<\/sub>) is given by<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71928\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-14.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"222\" height=\"58\" \/><\/p>\n<p><strong>Plane:<\/strong> A plane is a surface such that a line segment joining any two points of it lies wholly on it. A straight line which is perpendicular to every line lying on a plane is called a normal to the plane.<\/p>\n<p><strong>Equations of a Plane in Normal form<\/strong><br \/>\n<strong>Vector form:<\/strong> The equation of plane in normal form is given by \\(\\vec { r } \\cdot \\vec { n } =d\\), where \\(\\vec { n }\\) is a vector which is normal to the plane.<br \/>\n<strong>Cartesian form:<\/strong> The equation of the plane is given by ax + by + cz = d, where a, b and c are the direction ratios of plane and d is the distance of the plane from origin.<br \/>\nAnother equation of the plane is lx + my + nz = p, where l, m, and n are direction cosines of the perpendicular from origin and p is a distance of a plane from origin.<br \/>\nNote: If d is the distance from the origin and l, m and n are the direction cosines of the normal to the plane through the origin, then the foot of the perpendicular is (ld, md, nd).<\/p>\n<p><strong>Equation of a Plane Perpendicular to a given Vector and Passing Through a given Point<\/strong><br \/>\n<strong>Vector form:<\/strong> Let a plane passes through a point A with position vector \\(\\vec { a }\\) and perpendicular to the vector \\(\\vec { n }\\), then \\(\\left( \\vec { r } -\\vec { a } \\right) \\cdot \\vec { n } =0\\)<br \/>\nThis is the vector equation of the plane.<br \/>\n<strong>Cartesian form:<\/strong> Equation of plane passing through point (x<sub>1<\/sub>, y<sub>1<\/sub>, z<sub>1<\/sub>) is given by<br \/>\na (x \u2013 x<sub>1<\/sub>) + b (y \u2013 y<sub>1<\/sub>) + c (z \u2013 z<sub>1<\/sub>) = 0 where, a, b and c are the direction ratios of normal to the plane.<\/p>\n<p><strong>Equation of Plane Passing through Three Non-collinear Points<\/strong><br \/>\n<strong>Vector form:<\/strong> If \\(\\vec { a }\\), \\(\\vec { b }\\) and \\(\\vec { c }\\) are the position vectors of three given points, then equation of a plane passing through three non-collinear points is \\(\\left( \\vec { r } -\\vec { a } \\right) \\cdot \\left\\{ \\left( \\vec { b } -\\vec { a } \\right) \\times \\left( \\vec { c } -\\vec { a } \\right) \\right\\} =0\\).<br \/>\n<strong>Cartesian form:<\/strong> If (x<sub>1<\/sub>, y<sub>1<\/sub>, z<sub>1<\/sub>) (x<sub>2<\/sub>, y<sub>2<\/sub>, z<sub>2<\/sub>) and (x<sub>3<\/sub>, y<sub>3<\/sub>, z<sub>3<\/sub>) are three non-collinear points, then equation of the plane is<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71933\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-15.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"279\" height=\"89\" \/><br \/>\nIf above points are collinear, then<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71934\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-16.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"139\" height=\"87\" \/><\/p>\n<p><strong>Equation of Plane in Intercept Form:<\/strong> If a, b and c are x-intercept, y-intercept and z-intercept, respectively made by the plane on the coordinate axes, then equation of plane is \\(\\frac { x }{ a } +\\frac { y }{ b } +\\frac { z }{ c } =1\\)<\/p>\n<p><strong>Equation of Plane Passing through the Line of Intersection of two given Planes<\/strong><br \/>\n<strong>Vector form:<\/strong> If equation of the planes are \\(\\vec { r } \\cdot \\vec { { n }_{ 1 } } ={ d }_{ 1 }\\) and \\(\\vec { r } \\cdot \\vec { { n }_{ 2 } } ={ d }_{ 2 }\\), then equation of any plane passing through the intersection of planes is<br \/>\n\\(\\vec { r } \\cdot \\left( \\vec { { n }_{ 1 } } +\\lambda \\vec { { n }_{ 2 } } \\right) ={ d }_{ 1 }+\\lambda { d }_{ 2 }\\)<br \/>\nwhere, \u03bb is a constant and calculated from given condition.<br \/>\n<strong>Cartesian form:<\/strong> If the equation of planes are a<sub>1<\/sub>x + b<sub>1<\/sub>y + c<sub>1<\/sub>z = d<sub>1<\/sub> and a<sub>2<\/sub>x + b<sub>2<\/sub>y + c<sub>2<\/sub>z = d<sub>2<\/sub>, then equation of any plane passing through the intersection of planes is a<sub>1<\/sub>x + b<sub>1<\/sub>y + c<sub>1<\/sub>z \u2013 d<sub>1<\/sub> + \u03bb (a<sub>2<\/sub>x + b<sub>2<\/sub>y + c<sub>2<\/sub>z \u2013 d<sub>2<\/sub>) = 0<br \/>\nwhere, \u03bb is a constant and calculated from given condition.<\/p>\n<p><strong>Coplanarity of Two Lines<\/strong><br \/>\n<strong>Vector form:<\/strong> If two lines \\(\\vec { r } =\\vec { { a }_{ 1 } } +\\lambda \\vec { { b }_{ 1 } }\\) and \\(\\vec { r } =\\vec { { a }_{ 2 } } +\\mu \\vec { { b }_{ 2 } }\\) are coplanar, then<br \/>\n\\(\\left( \\vec { { a }_{ 2 } } -\\vec { { a }_{ 1 } } \\right) \\cdot \\left( \\vec { { b }_{ 2 } } -\\vec { { b }_{ 1 } } \\right) =0\\)<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71936\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-17.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"642\" height=\"130\" \/><\/p>\n<p><strong>Angle between Two Planes: Let \u03b8 be the <a href=\"https:\/\/infinitylearn.com\/surge\/maths\/angle-between-two-planes\/\" target=\"_blank\" rel=\"noopener\">angle between two planes<\/a>.<\/strong><br \/>\n<strong>Vector form:<\/strong> If \\(\\vec { { n }_{ 1 } }\\) and \\(\\vec { { n }_{ 2 } }\\) are normals to the planes and \u03b8 be the angle between the planes \\(\\vec { r } \\cdot \\vec { { n }_{ 1 } } ={ d }_{ 1 }\\) and \\(\\vec { r } \\cdot \\vec { { n }_{ 2 } } ={ d }_{ 2 }\\), then \u03b8 is the angle between the normals to the planes drawn from some common points.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71937\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-18.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"163\" height=\"85\" \/><br \/>\nNote: The planes are perpendicular to each other, if \\(\\vec { { n }_{ 1 } } \\cdot \\vec { { n }_{ 2 } } =0\\) and parallel, if \\(\\vec { { n }_{ 1 } } \\cdot \\vec { { n }_{ 2 } } =\\left| \\vec { { n }_{ 1 } } \\right| \\left| \\vec { { n }_{ 2 } } \\right|\\)<br \/>\n<strong>Cartesian form:<\/strong> If the two planes are a<sub>1<\/sub>x + b<sub>1<\/sub>y + c<sub>1<\/sub>z = d<sub>1<\/sub> and a<sub>2<\/sub>x + b<sub>2<\/sub>y + c<sub>2<\/sub>z = d<sub>2<\/sub>, then<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71938\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-19.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"288\" height=\"67\" \/><br \/>\nNote: Planes are perpendicular to each other, if a<sub>1<\/sub>a<sub>2<\/sub> + b<sub>1<\/sub>b<sub>2<\/sub> + c<sub>1<\/sub>c<sub>2<\/sub> = 0 and planes are parallel, if \\(\\frac { { a }_{ 1 } }{ { a }_{ 2 } } =\\frac { { b }_{ 1 } }{ { b }_{ 2 } } =\\frac { { c }_{ 1 } }{ { c }_{ 2 } }\\)<\/p>\n<p><strong>Distance of a Point from a Plane<\/strong><br \/>\n<strong>Vector form:<\/strong> The distance of a point whose position vector is \\(\\vec { a }\\) from the plane<br \/>\n\\(\\vec { r } \\cdot \\hat { n } =d\\quad is\\quad \\left| d-\\vec { a } \\hat { n } \\right|\\)<\/p>\n<p>Note:<br \/>\n(i) If the equation of the plane is in the form \\(\\vec { r } \\cdot \\vec { n } =d\\), where \\(\\vec { n }\\) is normal to the plane, then the perpendicular distance is \\(\\frac { \\left| \\vec { a } \\cdot \\vec { n } -d \\right| }{ \\left| \\vec { n } \\right| }\\)<br \/>\n(ii) The length of the perpendicular from origin O to the plane \\(\\vec { r } \\cdot \\vec { n } =d\\quad is\\quad \\frac { \\left| d \\right| }{ \\left| \\vec { n } \\right| }\\) [\u2235 \\(\\vec { a }\\) = 0]\n<p><strong>Cartesian form:<\/strong> The distance of the point (x<sub>1<\/sub>, y<sub>1<\/sub>, z<sub>1<\/sub>) from the plane Ax + By + Cz = D is<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71939\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-20.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"190\" height=\"73\" \/><\/p>\n<p><strong>Angle between a Line and a Plane<\/strong><br \/>\n<strong>Vector form:<\/strong> If the equation of line is \\(\\vec { r } =\\vec { a } +\\lambda \\vec { b }\\) and the equation of plane is \\(\\vec { r } \\cdot \\vec { n } =d\\), then the angle \u03b8 between the line and the normal to the plane is<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71940\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-21.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"134\" height=\"82\" \/><br \/>\nand so the angle \u03a6 between the line and the plane is given by 90\u00b0 \u2013 \u03b8,<br \/>\ni.e. sin(90\u00b0 \u2013 \u03b8) = cos \u03b8<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71941\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-22.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"137\" height=\"81\" \/><\/p>\n<p><strong>Cartesian form:<\/strong> If a, b and c are the DR\u2019s of line and lx + my + nz + d = 0 be the equation of plane, then<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-71942\" src=\"https:\/\/infinitylearn.com\/surge\/wp-content\/uploads\/2021\/12\/Three-Dimensional-Geometry-Class-12-Notes-Maths-Chapter-11-23.png\" alt=\"Three Dimensional Geometry Class 12 Notes Maths Chapter 11\" width=\"274\" height=\"64\" \/><br \/>\nIf a line is parallel to the plane, then al + bm + cn = 0 and if line is perpendicular to the plane, then \\(\\frac { a }{ l } =\\frac { b }{ m } =\\frac { c }{ n }\\)<\/p>\n<p><strong>Remember Points<\/strong><br \/>\n(i) If a line is parallel to the plane, then normal to the plane is perpendicular to the line. i.e. a<sub>1<\/sub>a<sub>2<\/sub> + b<sub>1<\/sub>b<sub>2<\/sub> + c<sub>1<\/sub>c<sub>2<\/sub> = 0<br \/>\n(ii) If a line is perpendicular to the plane, then DR\u2019s of line are proportional to the normal of the plane.<br \/>\ni.e. \\(\\frac { { a }_{ 1 } }{ { a }_{ 2 } } =\\frac { { b }_{ 1 } }{ { b }_{ 2 } } =\\frac { { c }_{ 1 } }{ { c }_{ 2 } }\\)<br \/>\nwhere, a<sub>1<\/sub>, b<sub>1<\/sub> and c<sub>1<\/sub> are the DR\u2019s of a line and a<sub>2<\/sub>, b<sub>2<\/sub> and c<sub>2<\/sub> are the DR\u2019s of normal to the plane.<\/p>\n<h5><\/h5>\n","protected":false},"excerpt":{"rendered":"<p>Direction Cosines of a Line: If the directed line OP makes angles \u03b1, \u03b2, and \u03b3 with positive X-axis, Y-axis [&hellip;]<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_yoast_wpseo_focuskw":"","_yoast_wpseo_title":"Three Dimensional Geometry Class 12 Notes Maths Chapter 11","_yoast_wpseo_metadesc":"CBSE Class 12 Maths Notes Chapter 11 Three Dimensional Geometry \u00b7 Straight line: \u00b7 Equation of Line Passing through Two Given Points \u00b7 Cartesian ...","custom_permalink":"study-materials\/three-dimensional-geometry\/class-12-notes\/maths-chapter-11\/"},"categories":[92,93,13,21],"tags":[],"table_tags":[],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO 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