Isosceles Triangle

An Isosceles triangle is the one which has two equal sides. Also, the two angles opposite to the two equal sides are equal. Suppose in a triangle △ABC, if sides AB and AC are equal, then △ ABC is an isosceles triangle where ∠ B = ∠ C.

Isosceles Triangle

The triangle having all the three sides equal are called as Equilateral triangle. Also, the triangle having all the three unequal sides is called as Scalene triangle. The images for both Equilateral and Scalene triangle is given below.

Isosceles Triangle types

Isosceles Triangle properties

Isosceles Triangle Properties

  1. As the two sides are equal in this triangle, the unequal side is called the base of the triangle.
  2. The angles opposite to the two equal sides of the triangle is always equal.
  3. The altitude of an isosceles triangle is measured from the base to the vertex(topmost ) of the triangle.
  4. A right isosceles triangle has third angle as 90 degree.

Isosceles Triangle Area

The area of an isosceles triangle is = ½ × b × h, where b is the base and h is the height of the triangle.

A = ½ × b × h

Example: Find the area of an isosceles triangle given its height as 6 cm and base as 4 cm?

Solution: Area of isosceles triangle is ½ × b × h

A = ½ × 4 × 6 = 12 cm2

Isosceles Triangle Perimeter

As we know the perimeter of any shape is the boundary of the shape. Similarly, perimeter of an isosceles triangle can be found if we know its base and side.

P = 2a + b, where ‘a’ are the two equal sides of the triangle and b is the base of the triangle.

Example: Find the perimeter of an isosceles triangle, with side 6 cm and base 4 cm.

Solution : P = 2a + b = 2(6) + 4 = 12 + 4 = 16 cm

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