Hello!

Q: With respect to an origin O, the points P and Q have position vectorspandqrespectively, given byp= (cos t)i+ (sin t)j-k,q= (cos 2t)i- (sin 2t)j+k, where t is a real parameter such that 0 < t < . Given thatpq= cos 3t - , hence or otherwise, find the greatest value of angle POQ.

Thank you for helping!