1. The problem statement, all variables and given/known data A particle , P moves on a horizontal plane along the circumference of a circle with centre O and a radius of 3m at an angular velocity of pi/4 rad/s in the clockwise direction . A second particle , Q moves on the same plane along a circle with radius 2m and the same centre as the first circle at an angular velocity of pi/2 rad/s in the clockwise direction . At first , O, P and Q are collinear with P and Q located at the north of O . Find the magnitude and direction of the velocity of P relative to Q . 2. Relevant equations 3. The attempt at a solution the angular displacement of P and Q are 3pi/4 and 3pi/2 respectively . The linear velocities of P and Q are 3pi/4 and pi respectively . then one of the angle of the triangle is 3pi/4 so i can use the cosine rule , |pVq|^2=pi^2+(3pi/4)^2-2pi(3pi/4)cos (3pi/4) |pVq|=5.49 m/s bu the answer given is 5.09 m/s where did i go wrong ?