For \(x\) between \(0\) and \(1\):

$$\text{atan}\frac{x}{1} \;+\; \text{atan}\frac{1-x}{1+x} \quad=\quad \alpha + \beta \quad=\quad 45^\circ$$

Trigono**graphy** Trig, if you will, the picture ...

For \(x\) between \(0\) and \(1\):

$$\text{atan}\frac{x}{1} \;+\; \text{atan}\frac{1-x}{1+x} \quad=\quad \alpha + \beta \quad=\quad 45^\circ$$