If each interior angle of a regular polygon is 135°, then find the number of diagonals of the polygon.

  1. 12
  2. 14
  3. 16
  4. 20

Answer (Detailed Solution Below)

Option 4 : 20
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Each interior angle of a regular polygon is 135,

⇒ Exterior angle = 180° - Interior angle = 45°

⇒ Number of sides of polygon = 360°/Exterior angle = 8

∴ Number of diagonals = n(n - 3)/2 = 8 × (8 - 3)/2 = 20, where n is the number of sides of a polygon.
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