Question

if sin3A= cos 60 what is the value of A

Answer 1

For acute angles
$\sin(3a) = \cos(60) \\ \sin(3a) = \sin(90 - 60) \\ \sin(3a) = \sin(30) \\ 3a = 30 \\ a = 10$

Answer 2

sin3A = cos60°

In trigonometry, there is a identity according to which if theta is in between 0° and 90° so value of cosA will be sin( 90 - A ).

sin3A = sin( 90 - 60 )°  

Comparing both the angles, both angles are sine angles so they are equal.

3A = 90° - 60°

3A = 3( 30° - 20° )

A = 30° - 20°

A = 10°

Therefore, value of A is 10°.

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