The value of cos²29^o + cos²61^o is:

Options
a) $ \frac {\sqrt 3}{2}$
b) 2
c) 0
d) 1

Solution

As per question
cos²29 + cos²61^o
cos²29 + (cos 61^o)²
cos²29 + (cos (90 – 29)^o)²
cos²29 + (Sin 29)²
Formula :- $ Sin \theta $ = cos (90 – $ \theta)$
cos²29 + sin²29 = 1
Formula :- $ sin^2 \theta + cos^2 \theta $ = 1

Ans is ) 1