Interior and Exterior Angles
Exterior Angles of a Polygon
Remember, a polygon is any shape that has 3 or more straight sides (no curves).
Click on the hexagon above to see that:
The exterior angles of any polygon add up to 360°
Interior Angles
90° + 60° + 30° = 180° | 80° + 70° + 30° = 180° |
It works for this triangle!
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Let's tilt a line by 10° ...
It still works, because one angle went up by 10°, but the other went down by 10°
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The Interior Angles of a Triangle add up to 180°
The interior angles in this triangle add up to 180° (90°+45°+45°=180°) | ... and for this square they add up to 360° ... because the square can be made from two triangles! |
Because a pentagon has three triangles, the sum of the interior angles add up to 3x180° = 540°
In general:
The sum of the interior angles of a polygon that has n sides, is:
(n-2) x 180°
Triangles in a circle:
The triangle drawn on the diameter of a circle is always
a right angled triangle