### Home > PC > Chapter 4 > Lesson 4.1.3 > Problem4-43

4-43.

For each angle (in radians) listed below, determine the signs of the coordinates in a unit circle.

1. $\frac { 4 \pi } { 7 }$

1. The denominator says the the top half of the circle should be divided into $7$ pieces.
2. The numerator says go to the 4th piece starting from ($1, 0$)
3. This angle is the 2nd quadrant so the signs are ($−, +$) for ($x, y$).

1. $- \frac { 3 \pi } { 5 }$

Move clockwise from ($1, 0$).

1. $\frac { 37 \pi } { 9 }$

Divide half of the circle into $9$ pieces. Every $18$ pieces is one time around the circle.

1. $−21\pi$

$-21π$ intersects the unit circle at the point ($-1, 0$), so the signs of the coordinates are ($-, 0$).