Geometry question regarding triangles and classification based on side lengths. Got this question wrong on a test and wanted to check to see if I was correct in my assumption.

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The terms isosceles and equilateral identify how many sides and how many angles are equal in a triangle so no, you would not use both terms for one triangle.

An isosceles triangle has two equal sides and two equal angles.

An equilateral triangle has three equal sides and three equal angles.

Definition: A triangle is isosceles if two sides are equal.

Definition: A triangle is equilateral if three sides are equal.

Every equilateral triangle is isosceles.

It is, however, quite possible for a triangle to be isosceles without being equilateral.

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