Given
- Triangles ABC and CDE are equilateral.
We need to
- Prove that AD and BE are congruent.
Solution
Since both the given triangles are equilateral, their interior angles are each measure 60°.
Consider triangles ADC and BEC.
We have:
- AC = BC (given)
- DC = EC (given)
- ACD = ACB + BCD = 60 + BCD (angle addition)
- ECB = ECD + BCD = 60 + BCD (angle addition)
According to above, two sides and the included angle of triangles ADC and BEC are congruent by ASA.
Therefore AD = BE as corresponding sides of congruent triangles, hence proved.