how do you solve this?

Question

   If cos65° = 0.4226, then sin25° =_____________. Explain the reasoning used to answer.  

Answer 1

If x is an angle then a basic trig identity is:

cos x = sin(90-x)

So when x = 65:

cos 65 = sin (90-65) = sin 25.

Thus sin 25 also equals 0.4226