CBSE Class 10 Maths (Standard) 2018 · Paper 30(B) · Question 18(b)

Triangles 3 marks Medium

In an equilateral

△ A B C

D

is a point on the side

B C

such that

B D = \frac{1}{3} B C

. Prove that

9 A D^{2} = 7 A B^{2}

Answer

A D^{2} = \frac{7 a ^{2}}{9}

, hence

9 A D^{2} = 7 A B^{2}

. Proved.

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