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转化思想是一种重要的数学思想.在求与圆有关阴影部分的面积时,通常对图形进行分解、组合,化不规则图形为规则图形,将阴影部分的面积转化为圆、扇形、三角形面积的和或差.现从2015年中考题精选几例,分别解析如下,供同学们参考.例1(2015年西宁卷)如图1,在半径为2,圆心角为90°的扇形内,以BC为直径作半圆交
The idea of transformation is an important mathematical thought. When seeking the area related to the shadow, we usually decompose, combine and form the irregular graph into a regular graph, convert the area of the shadow into a circle, a sector and a triangle And the difference or difference .Considering the 2015 mid-term exam selection a few cases, respectively, as follows, for the students reference .Example 1 (2015 Xining Volume) in Figure 1, in the radius of 2, the central angle of 90 ° sector , With BC as the diameter for semicircle