Question

which triangle is an isosceles triangle?

Explanation:

Step1: Recall isosceles - triangle definition

An isosceles triangle has at least two sides of equal length.

Step2: Analyze first triangle

The side - lengths are 5, 7, and 9. No two sides are equal.

Step3: Analyze second triangle

The side - lengths are 3, 3, and 3. It is an equilateral triangle (a special case of isosceles).

Step4: Analyze third triangle

The side - lengths are 6, 6, and some other length. It has two equal sides.

Answer:

The triangle with side - lengths 6, 6, and the third side is an isosceles triangle.