如图,在半径为R的圆形钢板上,冲去半径为r的四个小圆
题目
如图,在半径为R的圆形钢板上,冲去半径为r的四个小圆
,计算当R=7.8 cm,r=1.1 cm时阴影部分的面积(π取3.14).(利用因式分解)
答案
πR²-4πr²
=π(R²-4r²)
=π(R+2r)(R-2r)
=π(7.8+2*1.1)(7.8-2*1.1)
=π*10*5.6
=π*56
=175.84
=π(R²-4r²)
=π(R+2r)(R-2r)
=π(7.8+2*1.1)(7.8-2*1.1)
=π*10*5.6
=π*56
=175.84' ,rich:'0' });
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