RD Sharma Class 11 Solutions for Chapter 4: Measurement of Angles are an essential resource for students aiming to master the key concepts of angle measurement in the Class 11 Maths syllabus. This chapter, “Measurement of Angles,” introduces students to the foundational ideas of how angles are measured, the different systems used, and the importance of these concepts in trigonometry and geometry-making it a vital chapter for success in mathematics and competitive exams.
In RD Sharma Solutions for Class 11 Maths Chapter 4, you’ll find step-by-step solutions to all exercises, including detailed explanations for converting between degrees, radians, and grades. These solutions help clarify the difference between the sexagesimal (degree), centesimal (grade), and circular (radian) systems, and guide you through the logic behind each type of angle measurement. Each solution is designed to make even the most challenging problems approachable and easy to understand.
Student’s searching for a downloadable PDF of RD Sharma Chapter 4 Measurement of Angles, you’ll find comprehensive answers, solved examples, and extra questions to reinforce your understanding. The solutions cover all the important topics in the chapter, including the definition of an angle, systems of measurement, conversion formulas, and real-life applications such as finding the angle between clock hands or calculating arc length.
How to solve angle conversion problems in RD Sharma Class 11 Measurement of Angles? Our solutions walk you through the process, ensuring you can confidently convert between degrees, radians, and grades, and apply these concepts in practical situations. You’ll also find guidance on the relationship between angles and real numbers, and see how to solve application-based questions step by step.
For those needing help with standard problems and exam-focused questions, RD Sharma Class 11 Measurement of Angles solved examples and exercises providing visual explanations and practical tips. The content is fully aligned with the latest CBSE Class 11 Maths Chapter 4 syllabus, so you can be sure you’re preparing with the most relevant material.
Step 1: Recall the conversion formula from degrees to radians.
Step 2: Substitute 60° into the formula.
Radians = 60 × (π/180)
Step 3: Simplify the fraction.
60/180 = 1/3
Step 4: Complete the multiplication.
Radians = 1/3 × π = π/3
Answer: π/3 radians
Step 1: Recall the conversion formula from radians to degrees.
Step 2: Substitute π/6 into the formula.
Degrees = (π/6) × (180/π)
Step 3: Cancel out π in numerator and denominator.
Degrees = 180/6
Step 4: Simplify the fraction.
180/6 = 30
Answer: 30 degrees
Step 1: Convert radians to degrees using the formula.
Degrees = 1 × (180/π)
Step 2: Calculate the decimal value.
180/π ≈ 57.2958 degrees
Step 3: Separate the whole degrees.
Whole degrees = 57°
Step 4: Calculate the minutes from the decimal part.
Decimal part = 0.2958 × 60 = 17.748 minutes
Step 5: Separate whole minutes and calculate seconds.
Whole minutes = 17'
Decimal part = 0.748 × 60 = 44.88 seconds ≈ 45"
Answer: 57° 17′ 45″
Step 1: Use the conversion formula from degrees to radians.
Step 2: Substitute 150° into the formula.
Radians = 150 × (π/180)
Step 3: Simplify the fraction by dividing by common factor 30.
150/180 = 5/6
Step 4: Complete the calculation.
Radians = 5/6 × π = 5π/6
Answer: 5π/6 radians
Step 1: Use the conversion formula from radians to degrees.
Step 2: Substitute 3π/4 into the formula.
Degrees = (3π/4) × (180/π)
Step 3: Cancel out π in numerator and denominator.
Degrees = (3/4) × 180
Step 4: Calculate the result.
3 × 180 ÷ 4 = 540 ÷ 4 = 135
Answer: 135 degrees
Step 1: Recall the definition of a full circle.
A full circle is one complete rotation around a center point.
Step 2: Recall the standard measure for a full circle.
By definition, a full circle measures 360°.
Answer: 360 degrees
Step 1: Use the conversion formula to convert 360° to radians.
Step 2: Substitute 360° into the formula.
Radians = 360 × (π/180)
Step 3: Simplify the fraction.
360/180 = 2
Step 4: Complete the calculation.
Radians = 2 × π = 2π
Answer: 2π radians
Step 1: Recall the formula relating arc length, radius, and angle.
where θ is the angle in radians, s is arc length, and r is radius
Step 2: Identify the given values.
Arc length (s) = 11 cm
Radius (r) = 7 cm
Step 3: Substitute values into the formula.
θ = 11/7
Answer: 11/7 radians
Step 1: Recall the formula for arc length.
where s is arc length, r is radius, and θ is angle in radians
Step 2: Identify the given values.
Radius (r) = 10 cm
Angle (θ) = π/3 radians
Step 3: Substitute values into the formula.
s = 10 × (π/3)
Step 4: Calculate the result.
s = 10π/3 cm
Answer: 10π/3 cm
Step 1: Convert the angle from degrees to radians.
60° × (π/180) = 60π/180 = π/3 radians
Step 2: Recall the formula for sector area.
where A is area, r is radius, and θ is angle in radians
Step 3: Identify the values.
Radius (r) = 6 cm
Angle (θ) = π/3 radians
Step 4: Substitute values into the formula.
A = ½ × 6² × (π/3)
Step 5: Calculate step by step.
A = ½ × 36 × (π/3)
A = 18 × (π/3)
A = 18π/3 = 6π
Answer: 6π cm²
Step 1: Use the conversion formula from degrees to radians.
Step 2: Substitute 270° into the formula.
Radians = 270 × (π/180)
Step 3: Simplify the fraction by dividing by common factor 90.
270/180 = 3/2
Step 4: Complete the calculation.
Radians = 3/2 × π = 3π/2
Answer: 3π/2 radians
Step 1: Use the conversion formula from radians to degrees.
Step 2: Substitute 7π/6 into the formula.
Degrees = (7π/6) × (180/π)
Step 3: Cancel out π in numerator and denominator.
Degrees = (7/6) × 180
Step 4: Calculate the result.
7 × 180 ÷ 6 = 1260 ÷ 6 = 210
Answer: 210 degrees
Step 1: Recall the formula for arc length.
where s is arc length, r is radius, and θ is angle in radians
Step 2: Identify the given values.
Radius (r) = 4 cm
Angle (θ) = 2 radians
Step 3: Substitute values into the formula.
s = 4 × 2
Step 4: Calculate the result.
s = 8 cm
Answer: 8 cm
Step 1: Use the conversion formula from degrees to radians.
Step 2: Substitute 1° into the formula.
Radians = 1 × (π/180)
Step 3: Simplify the fraction.
Radians = π/180
Answer: π/180 radians
Step 1: Use the conversion formula from radians to degrees.
Step 2: Substitute 1 radian into the formula.
Degrees = 1 × (180/π)
Step 3: Calculate using π ≈ 3.14159.
180/3.14159 ≈ 57.2958
Answer: 57.3° (approx)
Step 1: Recall the formula relating arc length, radius, and angle.
where θ is the angle in radians, s is arc length, and r is radius
Step 2: Identify the given values.
Arc length (s) = 33 cm
Radius (r) = 21 cm
Step 3: Substitute values into the formula.
θ = 33/21
Step 4: Simplify the fraction by dividing by common factor 3.
33/21 = 11/7
Answer: 11/7 radians
Step 1: Recall the formula for sector area.
where A is area, r is radius, and θ is angle in radians
Step 2: Identify the given values.
Radius (r) = 7 cm
Angle (θ) = 2π/3 radians
Step 3: Substitute values into the formula.
A = ½ × 7² × (2π/3)
Step 4: Calculate step by step.
A = ½ × 49 × (2π/3)
A = 49/2 × (2π/3)
A = 49 × (π/3)
A = 49π/3
Answer: 49π/3 cm²
Step 1: First find the angle in radians using the formula.
Step 2: Substitute values.
θ = 15/5 = 3 radians
Step 3: Convert radians to degrees.
Step 4: Substitute the value.
Degrees = 3 × (180/π)
Step 5: Calculate using π ≈ 3.14159.
540/3.14159 ≈ 171.89°
Answer: 171.89°
Step 1: Use the conversion formula from radians to degrees.
Step 2: Substitute 2.5 radians into the formula.
Degrees = 2.5 × (180/π)
Step 3: Calculate the result.
2.5 × 180 = 450
Step 4: Divide by π.
450/π ≈ 450/3.14159 ≈ 143.24°
Answer: 143.24°
Step 1: Use the conversion formula from radians to degrees.
Step 2: Substitute 1.25 radians into the formula.
Degrees = 1.25 × (180/π)
Step 3: Calculate the result.
1.25 × 180 = 225
Step 4: Divide by π.
225/π ≈ 225/3.14159 ≈ 71.62°
Answer: 71.62°
Step 1: Use the conversion formula from degrees to radians.
Step 2: Substitute 330° into the formula.
Radians = 330 × (π/180)
Step 3: Simplify the fraction by dividing by common factor 30.
330/180 = 11/6
Step 4: Complete the calculation.
Radians = 11/6 × π = 11π/6
Answer: 11π/6 radians
Step 1: Recall the formula for arc length.
where s is arc length, r is radius, and θ is angle in radians
Step 2: Identify the given values.
Radius (r) = 14 cm
Angle (θ) = π/2 radians
Step 3: Substitute values into the formula.
s = 14 × (π/2)
Step 4: Calculate the result.
s = 14π/2 = 7π cm
Answer: 7π cm
Step 1: Convert the angle from degrees to radians.
45° × (π/180) = 45π/180 = π/4 radians
Step 2: Recall the formula for sector area.
where A is area, r is radius, and θ is angle in radians
Step 3: Identify the values.
Radius (r) = 10 cm
Angle (θ) = π/4 radians
Step 4: Substitute values into the formula.
A = ½ × 10² × (π/4)
Step 5: Calculate step by step.
A = ½ × 100 × (π/4)
A = 50 × (π/4)
A = 50π/4 = 25π
Answer: 25π cm²
Step 1: Use the conversion formula from degrees to radians.
Step 2: Substitute 90° into the formula.
Radians = 90 × (π/180)
Step 3: Simplify the fraction by dividing by common factor 90.
90/180 = 1/2
Step 4: Complete the calculation.
Radians = 1/2 × π = π/2
Answer: π/2 radians
Step 1: Recall the formula relating arc length, radius, and angle.
where θ is the angle in radians, s is arc length, and r is radius
Step 2: Identify the given values.
Arc length (s) = 5 cm
Radius (r) = 2 cm
Step 3: Substitute values into the formula.
θ = 5/2
Step 4: Calculate the result.
θ = 2.5 radians
Answer: 2.5 radians
The three primary systems of measuring angles introduced in Class 11 Maths are:
Sexagesimal System (Degree Measure) – Angles are measured in degrees (°), minutes (′), and seconds (″).
Centesimal System (Grade Measure) – Angles are measured in grades (g), where a right angle equals 100 grades.
Circular System (Radian Measure) – Angles are measured in radians, where the angle subtended at the center of a circle by an arc equal in length to the radius is 1 radian.
You can use the following standard formulas for conversions:
Degrees to Radians:
Radians = Degrees × (π/180)
Radians to Degrees:
Degrees = Radians × (180/π)
These formulas are extensively used in RD Sharma's Class 11 Chapter 4 problems and examples.
The radian is a natural unit of angular measure in mathematics because it relates arc length directly to radius without additional scaling. It simplifies calculus operations, especially derivatives and integrals involving trigonometric functions, and is used universally in advanced math, physics, and engineering due to its unit-free property.
You can find detailed step-by-step solutions to RD Sharma Class 11 Chapter 4 from:
Educational platforms like Infinity Learn and You can also refer to personalized walkthroughs and solved examples provided by your teacher or coaching notes.
Yes, most popular platforms and RD Sharma's latest editions are regularly updated to match the NCERT and CBSE Class 11 syllabus for 2024–25. The chapter "Measurement of Angles" aligns with the curriculum prescribed for Mathematics and is essential for foundational understanding in trigonometry.