Skill: Classify triangles by side length

To classify a triangle by its side lengths, compare the lengths of all three sides:

• Equilateral: all three sides are equal.
• Isosceles: exactly two sides are equal.
• Scalene: no sides are equal.

Example

A triangle has side lengths $6\text{ cm}$, $6\text{ cm}$, and $9\text{ cm}$. Classify the triangle.

1. List the side lengths: $6$, $6$, and $9$.
2. Compare the lengths. Two sides are equal: $6\text{ cm}=6\text{ cm}$.
3. The third side, $9\text{ cm}$, is different.
4. Therefore, the triangle is isosceles because it has exactly two equal sides.

The triangle’s position or appearance does not matter. Only the side lengths determine its classification.