Final answer:
The trajectory of a projectile is proven to be parabolic by solving for time in the horizontal motion equation and substituting it into the vertical motion equation, yielding an equation of the form y = ax + bx².
Step-by-step explanation:
To derive the parabolic trajectory of a projectile, we first solve the horizontal motion equation for time (t), which is expressed as t = x / v0x. We then substitute this expression for t into the vertical motion equation, y = v0yt - (1/2)gt2. This substitution yields the equation y = (v0y / v0x)x - (g / 2v0x2)x2. Upon simplification, we obtain an equation of the form y = ax + bx2, where a = v0y / v0x and b = -g / 2v0x2, thus showing that the trajectory is a parabola.