This is one of the two tired triangles of trig you should memorize. An isosceles right triangle has its sides in ratio [tex]1:1:\sqrt 2[/tex]. That means the hypotenuse is the square root of two times either side.
[tex] u = \sqrt{2} \times \sqrt{2} = 2[/tex]
Answer: C
If you didn't know you could write
[tex] v = \sqrt 2[/tex]
[tex]v^2 + v^2 = u^2[/tex]
[tex]u^2 = 2 + 2 = 4[/tex]
[tex]u = 2[/tex]
