Maths · Geometry and measures. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Most angle questions are solved with a few facts used one after another. Angles round a point, on a straight line and in a triangle have fixed totals. When a line crosses parallel lines it makes equal alternate angles and equal corresponding angles.
A polygon with n sides can be cut into n − 2 triangles, which gives the total of its interior angles. Its exterior angles always add to 360°. In a regular polygon all sides and all angles are equal. You also need the properties of special triangles and quadrilaterals.
A bearing is a direction given as an angle measured clockwise from north, written with three figures.
Dividing 360° by the number of sides gives the exterior angle of a regular polygon, not the interior angle. Subtract it from 180° to get the interior angle.
Answer: 115°
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