In triangle ABC, altitudes BE and CF are equal. Prove that the triangle is isosceles.
In Δ ABE and Δ ACF,
∠A = ∠A[Common]
∠AEB = ∠AFC = 90° [Given: BE AC; CF AB]
BE = CF [Given]
Δ ABE ≅ Δ ACF (AAS)
So AB=AC (Corresponding parts of Congruent Triangles)
Since two sides of triangle are equal,
Therefore, ABC is an isosceles triangle.