LEV K. answered • 12/14/19

Mid and High School Math and SAT prep

In regards with the angle. You need to consider the area as a function of 2 variables:

Area(y, θ) = y*(y-50)*sinθ

To find the extremum, you need to solve two equations:

partial derivative by y is 0: sinθ(50-2y)=0

partial derivative by θ is 0: (50-y)*y*cosθ = 0

Which gives y=25 (as in solution above) and θ=90^{º} So it is indeed a square with the side = 25