In an isosceles triangle, two sides are of equal length (originally and conventionally limited to exactly two).

Isoscel Triangle

An isosceles triangle has two equal angles: the angles opposite the two equal sides. The word isosceles is pronounced “eye-sos-ell-ease” with the emphasis on the ’sos’ – is any triangle that has two sides the same length. If all three sides are the same length it is called an equilateral triangle. The height of the isosceles triangle can be found from the Pythagorean theorem.

Isosceles Triangle Properties:

• The unequal side of an isosceles triangle is usually referred to as the ‘base’ of the triangle.
• The base angles of an isosceles triangle are always equal. In the figure above, the angles ∠ABC and ∠ACB are always the same
• The altitude is a perpendicular distance from the base to the topmost vertex.
• When the 3rd angle is a right angle, it is called a “right isosceles triangle”.