Polygons: interior and exterior angles
Plane geometry · Mathematics
Study notes
Q: Find each interior angle of a regular pentagon. How many sides if each exterior is 30°? Interior sum: (5-2)×180° = 540°. Each: 540°/5 = 108°. Exterior: 360°/n = 30°: n = 12 (dodecagon!). Check: interior = 150°, 150+30 = 180 ✓!