this is about special triangles and I don't understand I need help

in a 45-45-90 triangle, the sides are the same
you can find the third side using the pythagoran therum
[tex]a^{2} +b^{2} =c^{2}[/tex]
but a and b are the same thing, so
[tex]2x^{2} =c^{2}[/tex]
if x is the side
so, like in problem 1
[tex]2x^{2} =c^{2}\\2(25^{2}) =c^{2}\\2(625) =c^{2}\\1250 =c^{2}\\c=\sqrt{1250}\\c=35.36[/tex]
always make sure the hypotnus is longer than the legs