假如一个角是∠ABC.x0d另一角是∠DEFx0dAB//DEx0dBC//EFx0dx0d连接B点E点.定为MN线,如图:
![](http://h.hiphotos.baidu.com/zhidao/wh%3D600%2C800/sign=ba1e461673f082022dc799397bcbd7d5/810a19d8bc3eb13524af158ea61ea8d3fd1f449e.jpg)
x0d因为AB//DE.所以∠ABE=∠DENx0d因为BC//EF.所以∠CBE=∠FENx0d因为∠ABE=∠DEN.∠CBE=∠FEN.所以:∠ABC=∠DEFx0dx0d例2;连接B点E点.定为MN线,如图:
![](http://h.hiphotos.baidu.com/zhidao/wh%3D600%2C800/sign=6d2bc60ad9f9d72a1731181be41a040c/f9198618367adab43d8ab9768bd4b31c8701e4a9.jpg)
x0d因为AB//DE.所以∠ABN=∠DEM 两直线平行,内错角相等x0d因为BC//EF.所以∠CBN=∠FEN 两直线平行,平位角相等x0d因为∠DEF=180°-∠DEM-∠FENx0d ∠ABC=∠ABN+∠CBNx0d ∠ABN=∠DEMx0d ∠CBN=∠FENx0dx0d所以∠DEF=180°-∠ABC