Sorry for the delay. In case you still had questions about these, here's a few hints.

For 4.13, remember that $\tan(\theta)$ is equal to the opposite side divided by the adjacent side in a right triangle. Do you know a nice right triangle that has legs of length $3$ and $4$?

For 4.15, in a right triangle, $\sin(\theta)$ is equal to the opposite side divided by the hypotenuse. To try it out for this problem, what happens if you make the hypotenuse length $13$ and the opposite side length $11$. Can you find the third side of the right triangle?