Question

In ∆ABC, AB = 6√3cm. AC = 12 cm. and BC = 6 cm. The angle B is 

(A) 120° 

(b) 60° 

(C) 90° 

(D) 45°

Answer 1

Answer is (C) 90º

Here largest side is 12 cm. 

If square of the hypotenuse is equal to square of other two sides, then it is a right angled triangle. 

∴ c² = a² + b² 

AC² = AB² + BC²

(12)² = (63)² + (6)²

44 = 36 × 3 + 36 

144 = 108 + 36 

144 = 144 

∴ ∆ABC is a right angled triangle and angle opposite to hypotenuse, ∠B = 90°.