Learn Ncert All Solutions from a handpicked tutor in LIVE 1-to-1 classes

# 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

AB^{2} = 108 cm^{2}; AC^{2} = 144 cm^{2}; BC^{2} = 36 cm^{2}

AB^{2} + BC^{2} = (108 + 36) cm^{2}

= 144 cm^{2}

⇒ AC^{2} = AB^{2} +BC^{2}

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.

**☛ Related Questions:**

- D and E are points on the sides CA and CB respectively of a triangle ABC right angled at C. Prove that AE^2 + BD^2 = AB^2 + DE^2.
- The perpendicular from A on side BC of a ∆ABC intersects BC at D such that DB = 3CD (see Fig. 6.55). Prove that 2AB2 = 2AC2 + BC2.
- In an equilateral triangle ABC, D is a point on side BC such that BD = 1/3 BC. Prove that 9AD^2 = 7AB^2
- In an equilateral triangle, prove that three times the square of one side is equal to four times the square of one of its altitudes.

Math worksheets and

visual curriculum

visual curriculum