
已知:bp,cp分别是三角形abc的∠abc,∠acb的外角平分线bp,cp相交于点p,求∠bpc与∠a的数量关系说理由
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∠ABC+∠ACB=180-∠A
∠BCE+∠CBD
=180-∠ABC+180-∠ACB
=360-(∠ABC+∠ACB)
=360-(180-∠A)
=180+∠A
BP平分∠CBD,∠CBP=∠CBD/2
CP平分∠BCE,∠BCP=∠BCE/2
∠CBP+∠BCP
=(∠BCE+∠CBD)/2
=(180+∠A)/2
=90+∠A/2
∠BPC=180-(∠CBP+∠BCP)=180-(90+∠A/2)=90-∠A/2
∠BCE+∠CBD
=180-∠ABC+180-∠ACB
=360-(∠ABC+∠ACB)
=360-(180-∠A)
=180+∠A
BP平分∠CBD,∠CBP=∠CBD/2
CP平分∠BCE,∠BCP=∠BCE/2
∠CBP+∠BCP
=(∠BCE+∠CBD)/2
=(180+∠A)/2
=90+∠A/2
∠BPC=180-(∠CBP+∠BCP)=180-(90+∠A/2)=90-∠A/2
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