Question

How do I do this?

Express the following as trigonometric ratios of either 30, 45 or 60 degrees and hence find their exact values

A) sin120
B) cos225
C) tan390

Answer 1

A  sin120  = 2 sin60 cos 60  = 2 * sqrt3/2 * 1/2 =  sqrt3/2

B. cos 225 =  - cos 45 =  - 1 / sqrt2

C  tan 390 =  tan 30 =  1 / sqrt3