This is a 45-45-90 triangle which means that the two non-hyptonouse lenghts are the same which means that the bottom lenght of the triangle is also 10 units
We can then use a^2+b^2=c^2 to solve for the last side
so we have
10^2+10^2=x^2
200=x^2
sqrt200=x
and I see that they want an exact answer so you simplify sqrt200 to
