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1.合并求和法.把一个组合图形看成由几个常见的几何图形合并而成。先分别求出各部分面积,再相加,即得组合图形的面积。如图(1)即可看成“(?)+(?)”,半圆面积3.14×(2÷2)~2÷2与长方形面积3×2的和,即阴影部分面积。 2.去空求差法。如右图(2),把阴影部分面积看作扇形面积减去一个空白半圆面积。即“(?)-(?)=(?)” S_(阴影)=3.14×4~2×1/4-3.14×2~2÷2=6.28(平方厘米) 还有一种组合图形的阴影面积计算,既要“合并求和”又要“去空求差”。如下图,阴影部分面积要先把扇形和梯形面积合并求和,再减去空白直角
Amalgamation Summation A combination of graphics is considered as a combination of several common geometric shapes. First, respectively, to find the various parts of the area, and then add that is the area of the combination of graphics. (1) can be seen as “(?) + (?)”, The semicircle area of 3.14 × (2 ÷ 2) ~ 2 ÷ 2 and the rectangular area 3 × 2 sum, that is, the shadow area. 2. Empty for the difference method. As shown in the right picture (2), the shadow area is taken as the fan area minus a blank half area. That is, (?) - (?) = (?) “S_ (shading) = 3.14x4-2x1 / 4-3.14x2-2 / 2 = 6.28 (square centimeter) There is also a combination of the shadow area Calculation, it is necessary to ”merge the sum“ but also ”empty for difference." As shown below, the shaded area must first fan sector and trapezoidal area combined sums, minus the blank right angle