Equilateral Triangle Theorem

The Equilateral Triangle Theorem is a theorem which states that if all three sides of a triangle are equal, then all three angles are equal. It is a corollary of the Isosceles Triangle Theorem.

Proof

Assume a triangle ABC of equal sides AB, BC, and CA. By the ITT (Isosceles Triangle Theorem), m∠ABC = m∠BCA, m∠BCA = m∠CAB, and m∠CAB = m∠ABC.<ref>Euclid. The Elements. Book I.

See also

• Equilateral triangle