### Home > A2C > Chapter 12 > Lesson 12.3.1 > Problem12-125

12-125.

Give the exact value(s) for each of the unknowns (0 θ < 2π) in the equations below.

1. $\sin(\frac{3\pi}{4})=?$

Use the unit circle.

$\frac{\sqrt{2}}{2}$

1. $\cos(\frac{5\pi}{4})=?$

See part (a).

1. $\operatorname{tan}θ = 1$

$\text{Remember tan}\theta=\frac{\text{sin}\theta}{\text{cos}\theta}$

Where on the unit circle does sinθ = cosθ?

$\theta=\frac{\pi}{4},\,\frac{5\pi}{4}$

1. $\operatorname{tan}\left(θ\right) = −1$

See part (c).