Respuesta :

Aisin

Pythagorean theorem : [tex]a^{2} +b^{2} =c^{2}[/tex], c being the hypotenuse.

<=> [tex]x^{2} +19^{2} =21^{2}[/tex]

<=>x = [tex]\sqrt{21^{2}-19^{2} }[/tex] = 8.9