Thread: Find the exact value

1)

Attempt using the calculator

I am getting 120 degrees but should I take 120 degrees or the reference angle which is 60 as the answer?

Hi

therefore

Originally Posted by mj.alawami

1)

Attempt using the calculator

I am getting 120 degrees but should I take 120 degrees or the reference angle which is 60 as the answer?

Hi mj,

Cosine is negative in QII and QIII. Cos 120 = -1/2.

The angle in QIII would be Cos(240) = -1/2