Question drawn from very renowned book RD sharma of class 10th, Chapter no. 4
Chapter name:- Triangles
Exercise :- 4.2
This is very important question of triangle.
We have been given a triangle ΔABC,
In which D and E are points on the sides AB and AC respectively.
Now For following case we have to show that DE ∥ BC
Also it is given that AB = 5.6 cm, AD = 1.4 cm, AC = 7.2 cm, and AE = 1.8 cm.
learning CBSE maths in efficient way
RD sharma, DHANPAT RAI publication
Class 10th, triangle
Given:
Length of side AB = 5.6 cm, AD = 1.4 cm, AC = 7.2 cm, and AE = 1.8 cm
To show : Side DE is parallel to BC ( DE || BC )
Now,
Length of side BD = AB – AD = 5.6 – 1.4 = 4.2 cm
And,
Length of side CE = AC – AE = 7.2 – 1.8 = 5.4 cm
Now,
AD/BD = 1.4/4.2 = 1/3 – equation 1
AE/CE = 1.8/5.4 =1/3 – equation 2
Now from equation 1 and 2
AD/BD = AE/CE
So, by the converse of Thale’s Theorem
We get, DE ∥ BC.
Hence, Proved.