1. The problem statement, all variables and given/known data The distance between cities A and B it's L. An airplane flies back and forth between A and B, in a straight line, with velocity V in relation to the wind. So, calculate the total time of the flight, if the wind blows with velocity v, in a direction which forms an angle theta with direction AB. 2. Relevant equations x = x0 + v0*t v12 = v2 - v1 (relative velocity of 2 in relation to 1 is the difference between velocities 2 and 1 in relation to the origin). 3. The attempt at a solution Well, the time of the flight between A and B will be t = L/Ve (and I'm assuming that Ve is the velocity of the airplane in relation to the Earth). The back flight time will be different. I would calculate both times and add them both. But I don't know how to do this. The answer in my book is: https://www5b.wolframalpha.com/Calculate/MSP/MSP40222424iaf5566d1e00004f5598ab3d54c171?MSPStoreType=image/gif&s=12 [Broken] Any hints?