28,Công thức tính:
Chu vi: `C=2xx3,14xxR`
Diện tích: `S=3,14xxR^2`
Thay số:
Chu vi:
`R=0,5=>C=2xx3,14xx0,5=3,14`
`R=1=>C=2xx3,14xx1=6,28`
`R=1,5=>C=2xx3,14xx1,5=9,42`
`R=2=>C=2xx3,14xx2=12,56`
`R=2,5=>C=2xx3,14xx2,5=15,7`
`R=3=>C=2xx3,14xx3=23,55`
Diện tích:
`R=0,5=>C=3,14xx0,5^2=0,785`
`R=1=>C=3,14xx1^2=3,14`
`R=1,5=>C=3,14xx1,5^2=7,065`
`R=2=>C=3,14xx2^2=12,56`
`R=2,5=>C=3,14xx2,5^2=19,625`
`R=3=>C=3,14xx3^2=28,26`
\begin{array}{|c|c|c|}\hline \text{Bán kính R}&\text{Chu vi}&\text{Diện tích}\\\hline \text{0,5}&\text{3,14}&\text{0,785}\\\hline \text{1}&\text{6,28}&\text{3,14}\\\hline \text{1,5}&\text{9,42}&\text{7,065}\\\hline \text{2}&\text{12,56}&\text{12,56}\\\hline
\text{2,5}&\text{15,7}&\text{19,625} \\\hline \text{3}&\text{23,55}&\text{28,26}\\\hline\end{array}
