How do you know if sin 30° = sin 150°?

Sine is the primary trigonometric function. 

Answer: The value of sin 30° and sin 150° are equal.

Let's see how sin 30° = sin 150° is true.

Explanation:

We know that sin 30°  is 1/2.

We also know that sin (180° - θ ) = sin θ

sin (150°) = sin (180° - 30°) = sin 30°

So, sin 30° = sin 150° = 1/2

Since angle 30° lies in the first quadrant and angle 150° lies in the second quadrant, therefore the value of sin 150° is positive.

Thus, the value of sin 30° and sin 150° are equal.