Question

In an isosceles ∆ABC, if AC = BC and AB² = 2AC² , then ∠C = ? 

(a) 30°

(b) 45°

(c) 60°

(d) 90°

Answer 1

(d) 90°

Given: 

AC = BC 

AB² = 2AC² = AC² + AC² = AC² + BC² 

Applying Pythagoras theorem, we conclude that ∆ABC is right angled at C. 

Or, ∠C = 90°