What is equal to sin 30

From the unit circle sin 30 = sin pi/6 = 1/2.

The sine of any angle is equal to the cosine of the complementary angle.

Complementary angle means two angles whose total equal to 90 degrees.

The complementary angle for 30 degrees is 90 degrees - 30 degrees or 60 degrees.

So, sin (30) = cos (60).