(1)4除以2=2,2乘以2乘以π=4π
(2)4除以2=2,2乘以2乘以π=4π,4乘以4=16,16+4π
(3)周长:5乘以2乘以π=10π,10乘以2乘以π=20π,10π+20π=30π
面积:10乘以10乘以π-5乘以5乘以π=75π