### Home > PC3 > Chapter 2 > Lesson 2.3.1 > Problem2-128

2-128.

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 $4$th 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. $−21\pi$

$−21\pi$ intersects the unit circle at the point $(−1,0)$, so the signs of the coordinates are $(−,0)$.