​$$cos^231°+cos^259°$$​ is equal to:

Correct option is C

Given:

​$$\cos^2 31° + \cos^2 59°$$​​

Formula Used:

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

​$$\cos \theta = \sin(90° - \theta)$$​​

Solution:

​$$\cos^2 31° + \cos^2 59°$$​​

​$$=\sin^2(90° - 31°) + \cos^2 59°$$​​

​$$=\sin^2(59°) + \cos^2 59°$$​​

=1