Answer
a. $\theta$
b. $\pi - \theta$
c. $\theta - \pi$
d. $2\pi - \theta$
Work Step by Step
RECALL:
The reference angle $\hat{\theta}$ of an angle $\theta$, based on its terminal side's location, can be found using the following formulas:
Quadrant I: $\hat{\theta}=\theta$
Quadrant II: $\hat{\theta} = \pi - \theta$
Quadrant III: $\hat{\theta} = \theta - \pi$
Quadrant IV: $\hat{\theta} = 2\pi - \theta$
Thus, the missing expressions are:
a. $\theta$
b. $\pi - \theta$
c. $\theta - \pi$
d. $2\pi - \theta$
