### Home > CCA2 > Chapter 7 > Lesson 7.1.5 > Problem7-78

7-78.

Calculate each of the following values. Express your answers both exactly and as decimal approximations. Homework Help ✎

1. sin($\frac { \pi } { 4 }$)

2. sin($\frac { 2 \pi } { 3 }$)

Draw a unit circle and locate $\frac{\pi}{4}$ radians.

Remember that a full circle as 2π radians and a half circle has π radians.

How many degrees is equivalent to $\frac{\pi}{4}$ radians?

Draw a right triangle and use the special triangle relationship to find the exact value.

$\frac{\sqrt{2}}{2}$ or 0.707

Since $\pi$ is equivalent to $180^{^{\circ}}$$\frac{1}{3}$ of $\pi$ is $60^{^{\circ}}$.

What is $\frac{2}{3}$ of $\pi$? Locate $\frac{2\pi}{3}$  on the unit circle.

Draw a right triangle.
Notice that 60° is your reference angle.
Use the 30°-60°-90° relationship to find the exact value.