Respuesta :

gmany

Use the Pythagorean theorem:

[tex]|DF|^2+|EF|^2=|DE|^2[/tex]

We have |DF| = 12 and |DE| = 19. Substitute:

[tex]12^2+|EF|^2=19^2\\\\144+|EF|^2=361\qquad|-144\\\\|EF|^2=217\to|EF|=\sqrt{217}[/tex]

Answer: [tex]C.\ \sqrt{217}[/tex]