已知:如图,BG⊥BC,AC⊥BC,EF⊥AB,∠1=∠2,求证CD⊥AB.证明:∵DG⊥BC,AC⊥BC(___________)∴∠DGB=∠ACB=90º(垂直的定义)∴DG∥AC(_____________________)∴∠2=_____(_____________________)∵∠1=∠2(__________________)
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![已知:如图,BG⊥BC,AC⊥BC,EF⊥AB,∠1=∠2,求证CD⊥AB.证明:∵DG⊥BC,AC⊥BC(___________)∴∠DGB=∠ACB=90º(垂直的定义)∴DG∥AC(_____________________)∴∠2=_____(_____________________)∵∠1=∠2(__________________)](/uploads/image/z/2505401-17-1.jpg?t=%E5%B7%B2%E7%9F%A5%3A%E5%A6%82%E5%9B%BE%2CBG%E2%8A%A5BC%2CAC%E2%8A%A5BC%2CEF%E2%8A%A5AB%2C%E2%88%A01%3D%E2%88%A02%2C%E6%B1%82%E8%AF%81CD%E2%8A%A5AB.%E8%AF%81%E6%98%8E%EF%BC%9A%E2%88%B5DG%E2%8A%A5BC%2CAC%E2%8A%A5BC%28___________%29%E2%88%B4%E2%88%A0DGB%3D%E2%88%A0ACB%3D90%26%23186%3B%28%E5%9E%82%E7%9B%B4%E7%9A%84%E5%AE%9A%E4%B9%89%29%E2%88%B4DG%E2%88%A5AC%EF%BC%88_____________________%EF%BC%89%E2%88%B4%E2%88%A02%3D_____%28_____________________%29%E2%88%B5%E2%88%A01%3D%E2%88%A02%28__________________%29)
已知:如图,BG⊥BC,AC⊥BC,EF⊥AB,∠1=∠2,求证CD⊥AB.证明:∵DG⊥BC,AC⊥BC(___________)∴∠DGB=∠ACB=90º(垂直的定义)∴DG∥AC(_____________________)∴∠2=_____(_____________________)∵∠1=∠2(__________________)
已知:如图,BG⊥BC,AC⊥BC,EF⊥AB,∠1=∠2,求证CD⊥AB.
证明:∵DG⊥BC,AC⊥BC(___________)
∴∠DGB=∠ACB=90º(垂直的定义)
∴DG∥AC(_____________________)
∴∠2=_____(_____________________)
∵∠1=∠2(__________________)
∴∠1=∠DCA(等量代换)
∴EF∥CD(______________________)
∴∠AEF=∠ADC(____________________)
∵EF⊥AB ∴∠AEF=90º
∴∠ADC=90º 即CD⊥AB
已知:如图,BG⊥BC,AC⊥BC,EF⊥AB,∠1=∠2,求证CD⊥AB.证明:∵DG⊥BC,AC⊥BC(___________)∴∠DGB=∠ACB=90º(垂直的定义)∴DG∥AC(_____________________)∴∠2=_____(_____________________)∵∠1=∠2(__________________)
证明过程如下:
证明:∵DG⊥BC,AC⊥BC(已知)
∴∠DGB=∠ACB=90°(垂直定义)
∴DG∥AC(同位角相等,两直线平行)
∴∠2=∠ACD(两直线平行,内错角相等)
∵∠1=∠2(已知)
∴∠1=∠ACD(等量代换)
∴EF∥CD(同位角相等,两直线平行)
∴∠AEF=∠ADC(两直线平行,同位角相等)
∵EF⊥AB(已知)
∵∠AEF=90°(垂直定义)
∴∠ADC=90°(等量代换)
∴CD⊥AB(垂直定义).