The co-ordinates of a point on one trajectory relative to other will be
`x=x_(2)-x_(1)=(u_(2)cos theta_(@)-u_(1) cos theta_(1))t`
and
`y=(u_(2)sin theta_(2)t-(1)/(2)g t^(2))-(u_(1)sin tehta_(!)t-(1)/(2)g t^(2))`
`(u_(2)sin theta_(2)-u_(1)sin theta_(t))t`
So, `(y)/(x)=((u_(2) sin theta_(2)-u_(1)sin theta_(1))/(u_(2)cos theta_(2)-u_(1)cos theta_(1)))=` constt, =m
or y=mx which is a straight line