Question

evaluate
cos^2 20 + sin ^2 70/ sin^2 59 +sin^2 31

Answer 1

,.........................since cos(90-a)=sin a

Answer 2

I think your question is wrong it should be cos^2 20 + cos ^2 70/ sin^2 59 +sin^2 31

Hi mate here is your answer:

cos A = sin (90 - A)
sin A = cos (90 - A)
{cos2 20 + cos2 70}/{sin^2 59 + sin ^2 31}
= {cos220 + sin220}/{cos231 + sin259}
= 1 / 1 [as sin2 A + cos2 A = 1]
= 1
Hence answer is 1

I hope this will help you.