1. ## arctan question

$-\frac{\pi}{4}=arctan(\frac{\frac{-2L}{3}}{R})\\$
why it equals
$\frac{\frac{-2L}{3}}{R}=-1$
?

2. Originally Posted by transgalactic
$-\frac{\pi}{4}=arctan(\frac{\frac{-2L}{3}}{R})\\$
why it equals
$\frac{\frac{-2L}{3}}{R}=-1$
?
By taking "tan" for the both sides of the first equation.

3. I'm not sure what you are asking.

$\arctan(x)=-\pi/4$ has just one solution, which is $x=-1$.