Assume a projectile of mass m is projected with velocity u at an angle θ with the ground.
The horizontal component of the initial velocity is given as,
ux=ucosθ
The horizontal displacement at any time t is given as,
X=uxt
t=Xucosθ
The vertical component of the initial velocity is given as,
uy=usinθ
The horizontal displacement at any time t is given as,
Y=uyt−12gt2
Y=usinθ×Xucosθ−12g(Xucosθ)2
Y=Xtanθ−12g(Xucosθ)2
The above equation is a parabola.
Thus, the path of a projectile is parabolic.