1. ## Trig and Calculus:

The textbook I used didn't provide a detailed enough explanation.
How should I approach this problem?

2. ## Re: Trig and Calculus:

let $\arctan2(x,y)$ be the quadrant adjusted arc tangent of point $(x,y)$

$\theta = \arctan2(x,400)$

$\beta = \arctan2(x,225)$

$\alpha(x) = \theta-\beta = \arctan2(x,400)-\arctan2(x,225)$

$\dfrac {d \alpha}{dx}= \dfrac{225}{x^2+50625}-\dfrac{400}{x^2+160000}$

Now solve

$\dfrac {d \alpha}{dx} = 0$ for $x$