Răspuns :
[tex]A_{ABCD} = 2 * A_{ABC} = 2 * \frac{AB*AC}{2}[/tex]
In ΔABC : m∡(A)=90°
Aplicam teorema lui Pitagora:
AC² = BC² - AB²
AC² = 25² - 15²
AC² = 625 - 225
AC = √400
AC = 20
⇒ [tex]A_{ABCD} = 2* \frac{AB*AC}{2} = AB*AC= 15*20=300cm^{2}[/tex]