cos^-1 (cos 7π/6) is equal to:
(A) 7π/6   (B) 5π/6   (C) π/3   (D) π/6

Solution:

Inverse trigonometric functions as a topic of learning are closely related to the basic trigonometric ratios.

The domain (θ  value)  and the range(answer) of the trigonometric ratio are changed to the range and domain of the inverse trigonometric function.

Inverse trigonometric functions are the inverse ratio of the basic trigonometric ratios. 

Here the basic trigonometric function of Sin θ = y, can be changed to θ = sin^-1 y

cos^-1 (cos 7π / 6)

= cos^-1 (cos - 7π / 6)

= cos^-1 [cos (2π - 7π / 6)]

= cos^-1 [cos (5π / 6)]

= (5π / 6)

Thus,

the correct option is B

NCERT Solutions for Class 12 Maths - Chapter 2 Exercise 2.2 Question 19

cos^-1 (cos 7π/6) is equal to (A) 7π/6 (B) 5π/6 (C) π/3 (D) π/6

Summary:

cos^-1 (cos 7π/6) is equal to (5π / 6). Hence, the correct option is B. Inverse trigonometric functions as a topic of learning are closely related to the basic trigonometric ratios