In a triangle A B C , if | B C → | = 3 , | C A → | = 5 and | B A → | = 7 , then the…

In a triangle ABC, if |BC→|=3,|CA→|=5 and |BA→|=7, then the projection of the vector BA→ on BC→ is equal to
  1. 192
  2. 132
  3. 112
  4. 152

Solution

We have,

a→=3,b→=5,c→=7

Now,

cosθ=a→2+c→2-b→22a→c→

⇒cosθ=9+49-252·3·7

⇒cosθ=1114

Projection of c→ on b→

=|c→|cosθ

=7×1114

=112

Asked in: JEE Main 2021 (20 Jul Shift 2)

Practice more Vectors questions on Aicharya