Tick the correct answer and justify : In ∆ABC, AB = 6√3 cm, AC = 12 cm and BC = 6 cm. The angle B is :
(A) 120°  (B) 60°  (C) 90°  (D) 45°

Solution:

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

In ΔABC

AB = 6√3 cm; AC = 12 cm; BC = 6 cm

AB² = 108 cm²; AC² = 144 cm²; BC² = 36 cm²

AB² + BC² = (108 + 36) cm²

= 144 cm²

⇒ AC² = AB² +BC²

Pythagoras theorem satisfied. Thus, ∠ABC = 90°

Therefore, option (C) 90° is the correct answer.

☛ Check: NCERT Solutions Class 10 Maths Chapter 6

Video Solution:

Tick the correct answer and justify : In ∆ABC, AB = 6√3 cm, AC = 12 cm and BC = 6 cm. The angle B is : (A) 120° (B) 60° (C) 90° (D) 45°

NCERT Class 10 Maths Solutions Chapter 6 Exercise 6.5 Question 17

Summary:

For the given ∆ABC, AB = 63 cm, AC = 12 cm and BC = 6 cm. The angle B is 90 degrees.

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