Isosceles triangle is a triangle where
- Two sides are equal
- Angles opposite to equal sides are equal
Here,
- a is the side which is equal, AB = AC
- b is the base, BC = b
- Angles opposite to equal sides are equal, ∠B = ∠C ( Check Proof )
Perimeter
Perimeter of isosceles triangle = Sum of all sides
= a + a + b
= 2a + b
Perimeter of isosceles triangle = 2a + b
Properties of Isosceles triangle
- Two sides are equal
- Angles opposite to equal sides are equal
- Altitude is the median
∴ AD ⊥ BC
& D is the mid – point of BC