for this problem the steps are below
recall pythagorean theorem

where and and b are the legs of the right triangle and c is the hypotenuse

apply Pythagorean theorem

square each 4 and take the square root of both sides

simplify
reduce the radical
FINAL ANSWER

or you can simply see that it's a 45 45 90 triangle and know that the hypotenuse d equal one of the legs times the square root of 2