Answer:
angle 2 = 90° {corresponding angles}
angle 7 + angle 5 = 180° {linear pair}
or, angle 7 + 100° = 180° {angle 5 is corresponding to 100°}
so, angle 7 = 80°
All you need to do is add or subtract 2pi (a whole rotation) to the central angle. You add if you want to find the positive coterminal angles and you subtract to find the negative coterminal angles.
It should be FN because the upward force would be normal force.
