1) AC si BD sunt diagonalele patratului si sunt egale.
=> BD = AC = 5 cm
<BAC = 45°
2)
[tex]\displaystyle
-\frac{5}{16} : (-\frac{15}{16} )=\frac{5}{16} \times \frac{16}{15}=\frac{5 \times 16}{16 \times 15}= \frac{5 }{15}=\frac{1 }{3}[/tex]
3)
[tex]\displaystyle
\left(-\frac{5}{6}\right)^2 = \frac{5^2}{6^2} = \frac{25}{36}
[/tex]