Which of the following explains why Cosine 60 degrees = sine 30 degrees using the unit circle?

The sine and cosine are complementary functions.

Step-by-step explanation:

In a right angle triangle, the two angle angle are complementary.

This means they add up to 90 degrees.

One special property of the right angle triangle is that, the sine of angle is equal to the cosine of its complement.

On the unit circle we can also create a special right angle triangle with its hypotenuse being one unit.

The complementary property still applies to this right angle triangle.