ABC is an isosceles triangle in which AB = AC and D is a point on BC. Prove that AB^2 - AD^2 = BD * CD.?

'B' = 'C' by definition. 'A' is the hypotneuse. so anything that 'B' is, 'C' is exactly the same. so as long as the 'B(C) is a constant. the same variable will not alter it.