<-- Since y = x
If you are given one of the legs, you know the other one is equal to the given leg. If you are looking then for z then solve the above equation for z.
If you are given z then you know the two legs are equal and equal to x in the above equation. So solve it for x.
Example: You are given y = 5. Thus x = y = 5. And
Example: You are given z = 20. Thus
(Which simplifies to .)
Doing the other kinds of triangles involves a similar process, though, of course, x and y may not be equal. Either way we still have and you can work from there.