Hi! I attached one of my homework questions on optimization. I'm having a hard time understand why my answers are incorrect. I got pi/6 the first time and pi/2 the second time; but both of them are wrong. Please help! thank you!

IL} The trough in the gure is to be made to the dimensions shown. Only the angle 0 can be varied. What value of 0 will maximize the trough's volume? 0 = p112 radians Note: Webwork understands the functions "arcsin" and "arccos" . eview Answers Submit answers 1 have attempted this problem 2 times. 1r overall recorded score is 0%. [have 3 attempts remaining