## Special Names for Sides and Angles

**Legs, base, vertex angle, and base angles.** In an isosceles triangle, the two equal sides are called **legs,** and the third side is called the **base.** The angle formed by the two equal sides is called the **vertex angle.** The other two angles are called **base angles** (Figure 1).

** Figure 1 **Parts of an isosceles triangle.

In a right triangle, the side opposite the right angle is called the **hypotenuse,** and the other two sides are called **legs** (Figure 2).

**Figure 2 **Parts of a right triangle.