Given right triangle ABCABC with altitude \overline{BD}BD drawn to hypotenuse ACAC. If AC=19AC=19 and DC=4,DC=4, what is the length of \overline{BC}BC in simplest radical form? (Note: the figure is not drawn to scale.)
Lets call BD x. using pythagorean theorum, we have:
16+x^2+225+x^2=361
241+2x^2=361
x^2=60
x=$\boxed{2\sqrt{15}}$