Because the angles are both 45 degrees, the triangle is isosceles: the side lengths are equal. The hypotenuse of a model 45-45-90 triangle is √2 when the sides are 1 each:
√2 1
------ = -------
7√2 x
1 1
This can be reduced to ----- = -----
7 x
which makes it obvious that the side lengths are both 7.
