Answer
a. See graph.
b. $t=\frac{1}{4},\frac{3}{4},\frac{5}{4},\frac{7}{4}$; the light beam is parallel to the wall.
Work Step by Step
a. See graph.
b. The function will be undefined if $2\pi t=k\pi+\frac{\pi}{2}$ which gives $t=\frac{k}{2}+\frac{1}{4}$ where $k$ is an integer which gives $t$ in the interval of $[0,2]$. We can find that $t=\frac{1}{4},\frac{3}{4},\frac{5}{4},\frac{7}{4}$ when the function is undefined which means that the light beam is parallel to the wall.
