### Home > PC > Chapter 4 > Lesson 4.1.1 > Problem 4-7

4-7.

The reference angle is *π*/3. What are the cosine and sine of *π*/3? When writing your final answer, remember that this angle is in the fourth quadrant.

1. Draw a unit circle.

2. Divide the top and bottom halves into quarters.

3. Put a mark on the unit circle at the 5 quarters going clockwise from (1,0).

4. Make a triangle with the *x*-axis.

5. Label the lengths of the sides.

6. Check for the correct signs.

7. The coordinates are (*x*, *y*).

What are the side lengths? Use the Pythogorean Theorem.