PRINCIPIA · THEOREM

Equilateral ⇒ each angle 60°

Dependencies: Base angles of an isoceles triangle are equal, Triangle interior angles sum to 180°.

Statement

Let $\triangle ABC$ have all three sides equal: $AB = BC = CA$ . Then the three interior angles are all equal and each equals $60^\circ$ :

\angle A = \angle B = \angle C = 60^\circ.

$Equilateral triangle ABC: three sides equal ⇒ each angle is 60^\circ$

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