Test Index

Telangana TET Paper 2 Math and Science Model Paper 4

Section: Math and Science

Question : 125 of 150

Marks: +1, -0

The value of cos^{2}29° + cos^{2}61° is :

Solution:

Concept:

If two angles are complementary (sum = 90°), then the sum of the squares of their cosines equals 1. This uses the identity

\cos(90° - \theta) = \sin\theta

and

\sin^2\theta + \cos^2\theta = 1

Explanation:

Notice that

29° + 61° = 90°

, so the angles are complementary.

Rewrite

\cos^2 61°

\cos^2(90° - 29°) = \sin^2 29°

The given expression becomes

\cos^2 29° + \sin^2 29°

Using the Pythagorean identity,

\cos^2 29° + \sin^2 29° = 1

Thus, the value is 1.

Answer:

C. 1

Go to Question:

Prev Question

Next Question