Q.

The point (4,1) undergoes the following three transformations successively.

i) Reflection about the line x=y

ii) Translation through a distance 2 units along the positive direction of X - axis.

iii) Rotation through an angle π4 about the origin in the anti clockwise direction.

The final position of the point is given by the coordinates

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a

12,72

b

(2,72)

c

(2,72)

d

12,72

answer is C.

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Detailed Solution

Given, let P=(4,1)

i) Reflection (or image) of P(4,1) w.r.t to the line x+(1).y+0=0 is Q(say).

 By image formula we have=(h,k)

h41=k11=2(41+0)(1)2+(1)2=3

h=3+4=1;k=3+1=4

Q=(h,k)=(1,4)

ii) Given, a point Q(1,4) translated through a distance 2 units along the positive direction of x-axis.

Now, let new position of Q be R

Given, R lies on a line parallel to positive x-axis and the distance between Q, R is 2 units.

QR=2  and  R=(x,4)(x1)2+(0)2=4,RQ,

x1=2x=3

R=(3,4)

iii) Point R=(3,4)(In old system) ;  α=π4=angle of rotation

O=(0,0)=origin

OR=9+16=5

OR=5units

Question Image

Given ROS=45°=α=angle of rotation

Let XOR=θ. Here X is a point on positive x-axis

OR=OS=9+16=5

Question Image

Let XOR=θ

Given ROS=45°=α(say)

XOS=XOR+ROS

=θ+45°

cos(θ+45°)=cosθcos45°sinθsin45°

=(35)(12)(45)(12)

=4+352

=152

sin(θ+45°)=sinθcos45°+cosθsin45°

=45(12)+35(12)=752

Point S lies on the line OS such that OS=r=5

Parametric equation of line OS are

x=x1±rcosθ;y=y1±rsinθ

x=0±5(152);y=0±5(752)

x=±(1)2;y=±72

S=(12,72)  (or)  S=(12,72)

Since, cos(θ+45°)<0,sin(θ+45°)>0, we have (θ+45°)Q2

Slies in 2nd quadrant (Q2)

S=(12,72) is the required point

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