Question

Find A, if sin 5A=cos 4A; where 5A and 4A are acute angles.

Answer 1

According to the question :

sin a = cos(90-a)

sin 5a= cos 4a

so, sin 5a = cos ( 90 - 4a)

5a = ( 90 - 4a )

5a + 4a = 90

9a = 90

so, a = 10

the value of a = 10