Angles at a point are the angles formed around a common point, with their vertices coinciding at that point. The sum of angles at a point is always 360°.
This can be useful when solving problems involving angles around a point. For example, if we know three of the four angles formed around a point, we can find the fourth angle by subtracting the sum of the known angles from 360°.
Suppose we have angles A, B, C and D around point O, with angle A = 100°, angle B = 80°, and angle C = 120°. What is the measure of angle D?
Angles on a straight line are the angles created when two lines meet on a straight path. The point where they connect is called the vertex, and it’s also on the straight line. The sum of angles on a straight line is always 180°.
This rule is useful when solving problems involving supplementary angles or when determining the missing angle on a straight line.
If angle F = 45° and angle E = x, what is the measure of angle E?