Create a diagram of a right triangle with the light source at vertex L with acute angle Θ. The leg adjacent to Θ is perpendicular to the wall at point W, say, and the hypotenuse connects L to a 2nd point on the wall, P. We'll call the length of leg WP x and then we have the set-up we need to complete the related rates question:
dΘ/dt = 1 revolution/4 secs = 2π rads/ 4 secs = π/2 rads/sec , Θ = π/9
x = 11tanΘ
dx/dt = 11sec2Θ·dΘ/dt ~ 4.35 ft/sec
Josh F.
tutor
Oops. I may have accidentally typed in pi/9 instead of pi/2 for theta/dt into the calculator.
Try entering 11pi/(2cos^2(pi/9)) and see if that decimal is correct.
Maybe 19.58?
Report
03/08/21
Lily E.
I rounded it to one decimal point for 19.6! Thank you, that's right! :)
Report
03/08/21
Lily E.
Hello, it's showing on my end that 4.35 is incorrect.03/08/21