Each interior angle (regular) = ((n – 2) × 180°) / n.
Each exterior angle (regular) = 360° / n.
Triangles:
The sum of internal angles = 180°.
For any vertex, the corresponding external angle = 180° – (internal angle at that vertex).
This can help classify a triangle as acute (all interior < 90°), right (one interior = 90°), or obtuse (one interior > 90°).
This tool provides both interactive calculators and visual diagrams for exploring how internal and external angles work in regular polygons and in triangles – including custom analyses based on user inputs.