Answer:
x = sqrt(50) = 5sqrt(2) = 7.071 ft (to 3 decimals)
Step-by-step explanation:
referring to the diagram
theta (x) = atan(10/x) - atan(5/x)
differentiate with respect to x
theta'(x) = 5/(x^2+25) - 10/(x^2+100)
For x to have an extremum (max. or min)
theta'(x) = 0 ="
5/(x^2+25) - 10/(x^2+100) = 0
transpose and cross multiply
10(x^2+25) -5(x^2+100) = 0
expand and simplify
10x^2+250 - 5x^2-500 = 0
5x^2 = 250
x^2=50
x = sqrt(50) = 5sqrt(2) = 7.071 ft (to 3 decimals)
Since we know that if x becomes large, theta will decrease, so
x = 5sqrt(2) is a maximum.
