### Home > PC > Chapter 6 > Lesson 6.2.3 > Problem6-96

6-96.

If $\cos x = −\frac { 4 } { 5 }$, $x ∈ [π, \frac { 3 \pi } { 2 }]$ ($x ∈ [π, \frac { 3 \pi } { 2 }]$, means $x$ is an “element” of the set of all $x\text{'s}$ in the interval $[π, \frac { 3 \pi } { 2 }]$), find exact values for the five other trigonometric functions without finding $x$.

1. Draw the reference triangle in quadrant III.
2. Find all of the sides and label them.
3. Check to make sure the signs are correct.
4. Find the other trig functions from the sides of the reference triangle.