When the angle between two vectors of equal magnitude is `2pi//3`, prove that tha magnitude of the resultant is equal to either.

Explanation

`R=(P^(2)+Q^(2)+2PQ cos theta)^(1//2)`
`=(P^(2)+P^(2)+2P.P "cos"(2pi)/(3))^(1//2)`
`=[2P^(2)+2P^(2)((-1)/(2))]^(1//2)=P`