A missile is fired with a take-off speed of 120 m/s at an angle θ with respect to the ground. It experiences a horizontal acceleration of 50 m/s² along the x-axis in a direction opposite to the motion. Determine the value of θ so that the missile will cover the maximum distance.

Hint: use the following expression d/dθ(A•cosθ•sinθ - B•sin²θ) = A•cos(2θ) - B•sin(2θ)