Question

If `P+Q=R and |P|=|Q|= sqrt(3) and |R| ==3 ,` then the angle between P and Q is
A. `pi //4`
B. `pi//6`
C. `pi//3`
D. `pi//2`

Answer 1

Correct Answer - C
`(C) "Resultant"R=sqrt(P^(2)+Q^(2)+2PQcostheta)`
`3=sqrt((sqrt(3))^(2)+(sqrt(3))^(2)+2(sqrt(3))(sqrt(3))costheta)`
Squaring both sides
`9=3+3+6costheta`
`Costheta=(1)/(2)impliestheta=60^(@)Or (pi)/(3)`