Question

two vectors of equal magnitude have a resultant
equal to either of them in magnitude. The angle
between them is :
(1) 60° (2) 90° (3) 105° (4) 120°​

Answer 1

here is the solution of ur problem

Answer 2

ATQ

a(→) + a(→) = √ a²+ a²+2a²cosθ

but

given that

√ (a²+ a²+2a²cosθ) = a

=> 2a²+2a²cosθ= a²

=> 1+cosθ = 1/2

=> cosθ = -1/2

=> cosθ = cos120°

=> θ= 120°