Question

If cos A = 12/13 , and ∠A is in the fourth quadrant, find the exact value of sin2A.

Answer 1

Answer: 0.71

Explanation:

we have that cos(A) = 12/13

then:

A = Acos(12/13) = 22.62°

But A is in the fourth quadrant, so A is actually 22.62° + 180° = 202.62°

Then Sin(2A) = sin(2*202.62°) = 0.71