If is a triangle 90°, 45°, 45° then the sides are in ratio 1 : 1 : √2.
If c = 12 is a hypotenuse, therefore we have the equation:
[tex]a\sqrt2=12\ \ \ \ |\cdot\sqrt2\\\\2a=12\sqrt2\ \ \ \ |:2\\\\\boxed{a=6\sqrt2}[/tex]
If c = 12 is a leg, therefore we have:
[tex]\boxed{a=12\sqrt2}[/tex]
