podany kąt to kąt BWS
\sin\BWS=\frac{5}{13}
H=12
V=P_p+P_b
\frac{5}{13}=\frac{\frac{a}{2}}{h}
\frac{5}{13}=\frac{a}{2h}
10h=13a
h=1,3a
H^2=h^2-(\frac{a}{2})^2
144=(1,3a)^2-\frac{a^2}{4}
144=1,69a^2-\frac{a^2}{4}
576=6,76a^2-a^2
5,76a^2=576
a^2==100
a=10
h=1,3*10=13
$P_c=a^2+4\frac{1}{2}ah=a^2+2ah=10^2+10*13=100+130=230$$cm^2$