$b=-\sqrt{a^{2}-c^{2}}$
$b=\sqrt{a^{2}-c^{2}}$

$a=\sqrt{b^{2}+c^{2}}$
$a=-\sqrt{b^{2}+c^{2}}$

$b=\sqrt{a^{2}-c^{2}}$
$b=-\sqrt{a^{2}-c^{2}}\text{, }|a|\geq |c|$