Cześć ;-)
a)
[tex]\text{P}=\frac{1}{2}\cdot e\cdot f\\\\e=4 \ cm\\\\f=12 \ cm\\\\\text{P}=\frac{1}{2}\cdot4 \ cm\cdot12 \ cm=2 \ cm\cdot12 \ cm=\boxed{24 \ cm^2}[/tex]
b)
[tex]\text{P}=a\cdot h\\\\a=10 \ cm\\\\h=6,2 \ cm\\\\\text{P}=10 \ cm\cdot6,2 \ cm=\boxed{62 \ cm^2}[/tex]
c)
[tex]\text{P}=\frac{1}{2}\cdot(a+b)\cdot h\\\\a=12 \ dm\\\\b=8 \ dm\\\\h=9 \ cm=0,9 \ dm\\\\\text{P}=\frac{1}{2}\cdot(12 \ dm+8 \ dm)\cdot0,9 \ dm=\frac{1}{2}\cdot20 \ dm\cdot0,9 \ dm=10 \ dm\cdot0,9 \ dm=\boxed{9 \ dm^2}[/tex]
Pozdrawiam!
