If cos25° = 0.9063, then sin65° =_____________. Explain the reasoning used to answer this question.

Question

If cos25° = 0.9063, then sin65° =_____________. Explain the reasoning used to answer this question.

Answer 1

sin 65° = 0.9063

This is the reasoning: The sine of any acute angle is equal to the cosine of its complement. The cosine of any acute angle is equal to the sine of its complement. 

Complementary angles are 2 angles that add up to 90°. Since 25+65 = 90, these angles are complements.