### 11.4.3 The Unit Circle

This subsection is not completed yet, but in the meantime here are some practice questions.

Remember:
Since the $x$-coordinate of a point on the unit circle is the cosine of its angle, an equation like $\cos\theta=a$ can be visualised by intersecting the line $x=a$ with the unit circle: Similarly, $\sin\theta=a$ can be visualised by intersecting the line $y=a$ with the unit circle: And the equation $\tan\theta = a$ can be visualised by intersecting the unit circle with a line of slope $a$ (which passes through the point $(1,a)$ and the origin): Note that each equation has two solutions between $0$ and $2\pi$.