If v0 is the velocity of projection and α the angle of projection, the equation of trajectory is y = xtanα -
1
2
gx2
v02cos2α
..... (1) With origin at the point of projection, gx2 - 2v02 sinα cosαx + 2v02cos2αy = 0 ..... (2) Since the projectile passes through two points a,h and 2a,h , then a and 2a must be rootsof equation (2) a + 2a =