For 1.17, remember the midpoint is just the average of the x-coordinates and the average of the y-coordinates.

For 4.13, note that the values of the trig. functions only depend on the ratios between the sides. So based on the information (remember tangent is opposite / adjacent) we get assume that we have the following triangle:

For 4.30, the following (slightly messy) drawing hopefully helps:

What can you say about tan(55) and tan(75) in terms of x and y?