Not all 45-45-90 triangles have the sides 1, 1, sqrt(2). Do you know that?
Suppose what I said is wrong. That is suppose all 45-45-90 triangles have sides of length 1, 1 and Sqrt(2).
Now place this triangle on a copy machine and enlarge it. Obviously the sides will be larger but will the angles be the same? The answer is yes. So we have a 45-45-90 triangle where the sides are NOT 1, 1, sqrt(2). The thing is that the ratio of any two sides will be the same whether you use the enlarged triangle or the original triangle.
What do you multiply sqrt(2) by to get 2sqrt(14)? Whatever answer you get you should multiply 1, 1 and sqrt(2) by that number to get the length of the three sides.