Draw a straight line of length r = 25 m from the launch to the landing points, inclined at angle θ to the horizontal, as sketched below. Tilt the coordinate axes so that x is in the downhill direction of the incline, and y is perpendicularly outward from it. Suppose a rock is thrown with initial speed υi at launch angle ϕ above the incline, so that it follows the parabolic trajectory shown in red. The components of the gravitational acceleration are ax = gsinθ and ay = −gcosθ whereas the components of the initial velocity are υix = υicosϕ and υiy = υisinϕ.

The kinematic equations for the final position of the rock after a flight time tf from the launch to the landing points are

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