First, look at my attachment The dump truck makes imaginary right triangle.
From the right triangle, we can find the h with sin ratio of the triangle. h/b = sin of angle h = b × sin of angle (h stands for height, b stands for bed)
PART A: If the angle is 45° h = b × sin 45° h = 15 × 1/2√2 h = 15 × 0.707 h = 10.607 h = 10.6 The height is approximately 10.6 ft.
PART B: If the angle is 30° h = b × sin 30° h = 15 × 1/2 h = 7.5 The height is 7.5 ft.
PART C: If the angle is 60° h = b × sin 60° h = 15 × 1/2√3 h = 15 × 0.866 h = 12.990 h = 12.99 The height is approximately 12.99 ft.