Question

Two vectors of equal magnitudes have a resultant equal to either of them, then the angle between them will be
(a) 30°
(b) 120°
(c) 60°
(d) 150°
​

Answer 1

Explanation:

b) 120°

hope it helps you｡◕‿◕｡

Answer 2

Answer:

Applying the formula:

R2=P2+Q2+2PQcosα

P2=P2+P2+2PPcosα

=2P2+2P2cosα

=2P2(1+cosα)

1+cosα=

2

1

⇒2cos

2

2

α

=

2

1

⇒cos

2

2

α

=

4

1

⇒cos a/2= 1/2=cos60°

⇒ a/2=60°

⇒α=120°