
NCERT Solutions for Class 11 Maths Chapter 3 Exercise 3.1: NCERT Solutions for Class 11 Maths Chapter 3 Exercise 3.1 provide a detailed guide to understanding the foundational concepts of Trigonometric Functions.
This exercise focuses on topics such as angles, degree and radian measures, and their interrelation, along with the conversion between degrees and radians. These solutions are created to simplify complex concepts and provide step-by-step explanations, helping students strengthen their problem-solving skills.Class 11 Maths Chapter 3 Exercise 3.1 Questions and Answers PDF
1. Find the radian measures corresponding to the following degree measures:
(i) 25° (ii) – 47° 30′ (iii) 240° (iv) 520°
Solution:
(iv) 520°
2. Find the degree measures corresponding to the following radian measures (Use π = 22/7).
(i) 11/16
(ii) -4
(iii) 5π/3
(iv) 7π/6
Solution:
(i) 11/16 Here, π radian = 180°
(ii) -4
Here, π radian = 180°
(iii) 5π/3
Here, π radian = 180°
We get
= 300
o
(iv) 7π/6
Here, π radian = 180°
We get
= 210
o
3. A wheel makes 360 revolutions in one minute. Through how many radians does it turn in one second?
Solution:
It is given that No. of revolutions made by the wheel in 1 minute = 360 1 second = 360/60 = 6 We know that The wheel turns an angle of 2π radian in one complete revolution. In 6 complete revolutions, it will turn an angle of 6 × 2π radian = 12 π radian Therefore, in one second, the wheel turns at an angle of 12π radian.4. Find the degree measure of the angle subtended at the centre of a circle of radius 100 cm by an arc of length 22 cm (Use π = 22/7).
Solution:
5. In a circle of diameter 40 cm, the length of a chord is 20 cm. Find the length of the minor arc of the chord.
Solution:
The dimensions of the circle are Diameter = 40 cm Radius = 40/2 = 20 cm Consider AB as the chord of the circle, i.e., length = 20 cm
In ΔOAB,
Radius of circle = OA = OB = 20 cm
Similarly AB = 20 cm
Hence, ΔOAB is an equilateral triangle.
θ = 60° = π/3 radian
In a circle of radius
r
unit, if an arc of length
l
unit subtends an angle
θ
radian at the centre,
We get θ = 1/r
Therefore, the length of the minor arc of the chord is 20π/3 cm.
6. If in two circles, arcs of the same length subtend angles 60° and 75° at the centre, find the ratio of their radii.
Solution:
7. Find the angle in the radian through which a pendulum swings if its length is 75 cm and the tip describes an arc of length
(i) 10 cm (ii) 15 cm (iii) 21 cm
Solution:
In a circle of radius r unit, if an arc of length l unit subtends an angle θ radian at the centre, then θ = 1/r We know that r = 75 cm (i) l = 10 cm So we get θ = 10/75 radian By further simplification, θ = 2/15 radian (ii) l = 15 cm So, we get θ = 15/75 radian By further simplification, θ = 1/5 radian (iii) l = 21 cm So, we get θ = 21/75 radian By further simplification, θ = 7/25 radian