If the interior angle of a regular polygon is 108°, then it is a –

Concept: For a regular polygon with n sides, each exterior angle = 180° − interior angle, and the exterior angles always sum to 360°, so n = 360° ÷ exterior angle.

Application:

1. Given interior angle = 108°.

2. Exterior angle = 180° − 108° = 72°.

3. Number of sides, n = 360° ÷ 72° = 5.

Cross-check: For n = 5 (pentagon), interior angle = (n − 2) × 180° ÷ n = 3 × 180° ÷ 5 = 108°, which matches the given value — confirming the polygon is a pentagon.