Question

If `veca * vecb = 1/2 |veca| |vecb|`, then the angle between `veca` and `vecb` is ______.

Options

• 0°

• 30°

• 60°

• 90°

Answer 1

If `veca * vecb = 1/2 |veca| |vecb|`, then the angle between `veca` and `vecb` is 60°.

Explanation:

Given, `veca * vecb = 1/2 |veca| |vecb|`

`θ = cos^-1 [(veca * vecb)/(|veca||vecb|)]`

`θ = cos^-1 [(1/2 |veca||vecb|)/(|veca||vecb|)]`

`θ = cos^-1 [1/2]`

θ = cos^–1 [cos 60°]

θ = 60°