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添辅助线法求组合图形的面积

添辅助线法求组合图形的面积. 宁波市鄞州区东湖小学 张明菲. 添辅助线法求组合图形的面积. 例1： 三角形CDE的面积是5平方厘米，BD=3CD，AE=EC。求三角形ABC的面积。. S △BCE = 5 ×2 = 10 cm 2. S △ABC = 10 ×2 = 20 cm 2. 5. 添辅助线法求组合图形的面积. 例2： AE将平行四边形ABCD分为两部分，两部分的面积相差15平方厘米 ， EC =（ ）cm。. F. 15÷5 = 3cm. 15. 添辅助线法求组合图形的面积.

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添辅助线法求组合图形的面积

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  1. 添辅助线法求组合图形的面积 宁波市鄞州区东湖小学 张明菲

  2. 添辅助线法求组合图形的面积 例1：三角形CDE的面积是5平方厘米，BD=3CD，AE=EC。求三角形ABC的面积。 S△BCE= 5×2 = 10 cm2 S△ABC= 10×2 = 20 cm2 5

  3. 添辅助线法求组合图形的面积 例2：AE将平行四边形ABCD分为两部分，两部分的面积相差15平方厘米，EC =（ ）cm。 F 15÷5 = 3cm 15

  4. 添辅助线法求组合图形的面积 例3：在长方形ABCD中，△ABG的面积是16平方厘米，△CDH的面积是24平方厘米，阴影部分面积是多少平方厘米？ S△ABG= S△EFG S△EFH= S△CDH 16 24 16＋24 = 40cm2

  5. 添辅助线法求组合图形的面积 例4：ABCG是长为7厘米，宽为4厘米的长方形，DEFG是长为10厘米，宽为2厘米的长方形。那么三角形BCM的面积与三角形DEM的面积之差是多少平方厘米？ 7 S△BHE= 3×6÷2 = 9 cm2 4 S□CDEH = 3×2 = 6 cm2 2 S△BCM － S△DEM = 9－6 = 3cm2。 H 10 HE=10－7= 3 cm BH= 4＋2= 6 cm

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