Hi! I was doing some exercises about the doppler effect on sound untill I found this problem that I can't find the solution! "A source of sound of frequency f0 moves horizontally at constant speed u in the x direction at a distance h above the ground. An observer is situated on the ground at the point x=0 (the source passes over this point at t=0). Show that the signal received at any time Tr at the ground was emitted by the source at an early time Ts , such that: [1-(u/v)2]*Ts=Tr-(1/v)√(h2*[1-(u/v)2]+u2*Tr2) where v is the speed of the sound." Can someone please help me and explain this exercise to me? I have been trying to solve it for 48 hours and I just can't! -.- Thank you!