ABC is a triangle in which BE and CF are, respectively, the perpendiculars to the sides AC and AB. If BE = CF, prove that ΔABC is isosceles.
Given : In ΔABC,
BE ⊥ AC and CF ⊥ AB
BE=CF
To prove : ΔABC is an isosceles triangle
Proof : In right ΔBCE and ΔBCF
Side BE = CF (Given)
Hyp. BC = BC (Common)
∴ Δ BCE≅ ΔBCF (RHS axiom)
∴ ∠BCE=∠CBF (c.p.c.t.)
∴ AB=AC (Sides opposite to equal angles)
∴ Δ ABC is an isosceles triangle