Skill: Classify triangles by side lengths

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: all three sides are different.

The triangle’s position or shape in a picture does not matter. Use the side measurements.

Example: A triangle has side lengths $6\text{ cm}$, $6\text{ cm}$, and $4\text{ cm}$.

1. List the side lengths: $6$, $6$, and $4$.
2. Compare them. Two sides have the same length: $6\text{ cm}=6\text{ cm}$.
3. The third side, $4\text{ cm}$, is different.
4. Since exactly two sides are equal, the triangle is isosceles.