Question

In an equilateral triangle ABC, D is a point on side BC such that BD=1/3 BC Prove that 9AD² = 7AB²

Answer 1

Given: An equilateral triangle ABC and D be a point on BC such that BD=1/3 BC.

To Prove: 9AD² = 7AB²
Construction: Draw AE ⊥ BC.
Proof: ∆ABC is an equilateral triangle and AEBC= BE = EC
Thus, we have