Correct Answer - Option 3 : 90°
Given:
AB, BC and AC are the three sides of ΔABC of length 6√3 cm, 6 cm and 12 cm respectively
Concept used:
If in a ΔABC, AB2 + BC2 = AC2
Then ΔABC is a rightangle triangle with ∠B = 90°
Calculation:
According to the concept, we have
AB2 + BC2 = {(6√3)2 + 62} cm2
⇒ (108 + 36) cm2
⇒ 144 cm2 ----(1)
And, AC2 = 122 cm2
⇒ 144 cm2 ----(2)
Here, equation (1) = equation(2)
So, AB2 + BC2 = AC2
∴ ∠B is 90°.