Rotating Light in calculus

Question

A rotating light is located 12 feet from a wall. The light completes one rotation every 4 seconds. Find the rate at which the light projected onto the wall is moving along the wall when the light's angle is 25 degrees from perpendicular to the wall.

Answer is a positive value. Give your answer accurate to at least one decimal place.

? feet per second

Answer 1

x = 12tanθ; dx/dt = 12sec²θdθ/dt = 12sec²25°·2π/4 = 22.95 ft/s