Question

Oblicz obwód koła o podanym polu.

a)100 pi cm2

b)900 pi cm2

c)0,64 pi cm2

Answer 1

a)P=100πcm²

4πr²=100π /:4π

r²=25

r=√25=5cm

l=2πr=2·5π=10πcm

 

b)P=900πcm²

4πr²=900π /:4π

r²=225

r=√225=15cm

l=2·15π=30ππcm

 

c)P=0,64πcm²

4πr²=0,64π  /:4π

r²=0,16

r=√0,16=0,4cm

l=0,4·2π=0,8πcm