silemus.
← All examples
  1. 9Similar triangles, shadows
  2. 10Similar triangles, area ratio
  3. 1230-60-90 triangle sides
  4. 14Angle of elevation, right triangle
  5. 18Inscribed angle theorem
  6. 19Angle in a semicircle
  7. 21Equal tangent lengths
  8. 22Chord distance from centre
  9. 26Interior angles of an octagon
  10. 30Area and side of a rhombus
  11. 31Prism volume and surface area
  12. 33Volume and slant height of cone
  13. 40Perpendicular bisector
  14. 41Area of triangle by coords
  15. 42Circle, completing the square

26Interior angles of an octagon

Find the sum of the interior angles of an octagon, and the size of each interior angle of a regular octagon.

The interior angles of an octagon sum to 1080°, and each angle of a regular octagon is 135°. Using (n−2)×180° with n=8 gives (8−2)×180° = 1080°, then 1080°÷8 = 135° per angle. Check: 8×135° = 1080°.

How good is this answer?