Question

congruent triangles quiz
which of the following statements is incorrect?
the isosceles triangle theorem can be applied to equilateral triangles
a triangle with three congruent angles is equilateral.
a triangle with three congruent sides is equiangular.
the measure of each angle of an equilateral triangle is 120°.

Explanation:

1. The Isosceles - Triangle Theorem can be applied to equilateral triangles since equilateral triangles are a special case of isosceles triangles.
2. A triangle with three congruent angles (each 60°) is equilateral by the angle - side relationship in triangles.
3. A triangle with three congruent sides is equiangular, which is a well - known property of equilateral triangles.
4. The sum of the interior angles of a triangle is 180°. For an equilateral triangle, each angle is $\frac{180^{\circ}}{3}=60^{\circ}$, not 120°.

Answer:

The measure of each angle of an equilateral triangle is 120°.