Question taken from RD sharma

Class 10th

Chapter no. 4

Chapter name:- Triangles

Exercise :- 4.3

This is very basic and important questions.

It is given that In a ∆ABC, AD is the bisector of ∠A, meeting side BC at D

Also If AB = 10 cm, AC = 6 cm and BC = 12 cm,

Now we have to find BD and DC

Understanding and learning CBSE maths

RD sharma, DHANPAT RAI publication

Since, AD is the bisector of ∠ A meeting side BC at D in Δ ABC

⇒ AB/ AC = BD/ DC

10/ 6 = BD/ DC …….. (i)

And, we know that

BD = BC – DC = 12 – DC

Let BD = x,

⇒ DC = 12 – x

Thus (i) becomes,

10/ 6 = x/ (12 – x)

5(12 – x) = 3x

60 -5x = 3x

∴ x = 60/8 = 7.5

Hence, DC = 12 – 7.5 = 4.5cm and BD = 7.5 cm