Wzor na pole rombu:
[tex]P = \frac{ef}{2}\\e = d_1\\f=d_2\\P=\frac{d_1d_2}{2}\\20cm^2=\frac{2cm*d_2}{2} /*2\\40cm^2=2cm*d_2 /:(2cm)\\\frac{40cm^2}{2cm}=d_2\\20cm=d_2[/tex]
