If sin theta = - (sqrt (3)) / 2 and pi < = theta < = (3pi) / 2, determine the value of cos (20)

Sin theta = - 1/2

Step-by-step explanation:

pi < = theta < = (3pi) / 2.

The above expression shows we are dealing with angle on the 3rd quadrant.

I. e greater than 180 but less than 270.

So sin tita = (√3) / 2

But sin and cos are all negative in the third quadrant.

So tita = sin^-1 (√3) / 2

tita = 60°

Cos tita = cos 60

Cos tita = cos 60

Cos60 = 0.5

Cos 60 = 1/2

If

sin theta = - (sqrt (3)) / 2

Sin theta = - 1/2