Question

Prove in a triangle, if the square of one side is equal to the sum of the squares of the other two sides, then the angle opposite to the first side is a right angle.

Answer 1

Given: A triangle ABC in which AC² = AB² + BC².
To Prove: ∠B = 90°.

Construction: We construct a ΔPQR right-angled at Q such that PQ = AB and QR = BC
Proof: Now, from ΔPQR, we have,