When performing synthetic division, the divisor is a "zero" of the function. This means it is an x-intercept. To figure out what the factor is associated with this x-intercept, we determine what we would do to the factor to make it equal 0. In this case, we would add 5; this makes our factor, or divisor, x+5.
If you're looking for an angle in between those, basically you have to choose an angle between 0 and 90°. any angle should work (such as 15°, 45°, 60°, 75°, etc.)
