ããé¿æ¹å½¢é¢ç§¯=åçé¢ç§¯ï¼é¿æ¹å½¢çé¿=åçå¨é¿çä¸å=16.8÷2=8.4cmï¼å®½=åçåå¾ï¼
ããé´å½±çå¨é¿=BC+AB+CD+AD弧é¿=åçå¨é¿+1/4åå¨é¿=16.8+16.8Ã1/4=16.8+4.2=21cm
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C₁=πd 16.4÷3.14=5.2
r=d/2 5.2÷2=2.6
S₁=π×r² 3.14×2.6²=21.22
S₂=ab 21.22÷2.6=8.16
C₂=8.16+8.16+16.4÷4=20.42