We have a right triangle with hypotenuse 38 and leg 34.
We want to find the other leg.
We use the Pythagorean Theorem:
\(a^{2}+b^{2}=c^{2}\)
\(\Rightarrow a^{2}+34^{2}=38^{2}\)
\(\Rightarrow a^{2}+1156=1444\)
\(\Rightarrow a^{2}=288\)
\(\Rightarrow a=12\sqrt{2}\approx 17.0\)