∵∠ABC=90,PA⊥平面ABC
∴BC⊥AB,BC⊥AP
∴BC⊥平面ABP,又∵AM在平面ABP内
∴AM⊥BC,又AM⊥BP
∴AM⊥平面PBC,又AM在平面AMN内
∴平面AMN⊥平面PBC
∵AM⊥平面PBC,AN⊥PC
∴MN⊥PC(三垂线定理)
角ABC等于九十度,PA垂直ABC,垂足为A,AM垂直PB,AN垂直PC,垂足分别为M、N,连结MN.求证平面AMN垂直...
角ABC等于九十度,PA垂直ABC,垂足为A,AM垂直PB,AN垂直PC,垂足分别为M、N,连结MN.求证平面AMN垂直...
角ABC等于九十度,PA垂直ABC,垂足为A,AM垂直PB,AN垂直PC,垂足分别为M、N,连结MN.求证平面AMN垂直平面PBC,MN垂直PC
角ABC等于九十度,PA垂直ABC,垂足为A,AM垂直PB,AN垂直PC,垂足分别为M、N,连结MN.求证平面AMN垂直平面PBC,MN垂直PC
数学人气:334 ℃时间:2020-03-09 13:29:55
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