如图，△ABC是直角三角形，AB为圆直径，AB=20，阴影I的面积比阴影Ⅱ的面积大7，求BC的长．
﹣=+= 1﹣=+= 1﹣=+=
填一填．
直接写得数．+=﹣= 0.2﹣=+=﹣=+2÷9= 2﹣﹣= 1.55﹣= 1﹣﹣+= 0.5﹣﹣=
计算．===== 1﹣===
看图计算下面各题．+= +=
﹣
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= 1﹣
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= 1﹣
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﹣
= 0.2﹣
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﹣
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+2÷9=
﹣
= 1.55﹣
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= 1﹣
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