锟斤拷锟斤拷锟斤拷锟狡斤拷锟斤拷锟揭伙拷l直锟斤拷锟斤拷平锟斤拷锟�(n锟斤拷i)锟斤拷一锟絣直锟斤拷平锟斤拷锟斤拷锟斤拷锟紷么直锟斤拷锟酵猴拷平锟斤拷平锟斤拷锟斤拷锟斤拷(ji锟斤拷n)锟斤拷之锟斤拷锟斤拷锟斤拷平锟斤拷锟斤拷锟絫锟斤拷锟斤拷平锟斤拷锟斤拷同锟絩(sh锟斤拷)锟斤拷要锟紺锟斤拷锟斤拷锟斤拷平锟叫ｏ拷锟酵碉拷锟斤拷平锟斤拷锟�(n锟斤拷i)锟斤拷一锟絣锟斤拷锟斤拷使锟矫撅拷锟斤拷平锟斤拷锟斤拷

锟斤拷锟斤拷1锟斤拷锟斤拷平锟叫碉拷锟叫讹拷锟斤拷锟斤拷

锟斤拷锟斤拷锟斤拷锟斤拷1

锟斤拷锟斤拷平锟斤拷锟斤拷一锟絣直锟斤拷锟絚锟斤拷平锟斤拷锟�(n锟斤拷i)锟斤拷一锟絣直锟斤拷平锟斤拷锟斤拷锟絫該直锟斤拷锟絚锟斤拷平锟斤拷平锟斤拷锟斤拷

锟斤拷锟斤拷锟斤拷知锟斤拷a锟斤拷b锟斤拷a?α锟斤拷b?α锟斤拷锟斤拷锟紺锟斤拷a锟斤拷α

锟斤拷锟斤拷锟斤拷锟紺锟斤拷锟紺锟斤拷锟斤拷锟斤拷锟絆(sh锟斤拷)a锟絚α锟斤拷平锟斤拷锟斤拷锟絫锟斤拷锟斤拷锟洁交锟斤拷锟絆(sh锟斤拷)锟斤拷锟絚(di锟斤拷n)锟斤拷A锟斤拷锟斤拷么A∈α

锟斤拷锟斤拷锟斤拷a锟斤拷b锟斤拷∴A锟斤拷锟斤拷b锟斤拷

锟斤拷锟斤拷锟斤拷α锟斤拷(n锟斤拷i)锟絕A锟斤拷c锟斤拷b锟斤拷锟絫a∩c=A

锟斤拷锟斤拷锟街★拷a锟斤拷b锟斤拷b锟斤拷c锟斤拷∴a锟斤拷c锟斤拷锟絚a∩c=A矛锟斤拷锟斤拷

锟斤拷锟斤拷∴锟斤拷锟絆(sh锟斤拷)锟斤拷锟斤拷锟斤拷锟斤拷a锟斤拷α

锟斤拷锟斤拷锟斤拷锟斤拷锟斤拷锟紺锟斤拷锟斤拷锟絆(sh锟斤拷)a锟侥凤拷锟斤拷锟斤拷锟斤拷锟斤拷a锟斤拷b锟侥凤拷锟斤拷锟斤拷锟斤拷锟斤拷b锟斤拷锟斤拷α锟侥凤拷锟斤拷锟斤拷锟斤拷p锟斤拷锟斤拷b?α

锟斤拷锟斤拷∴b⊥p锟斤拷锟斤拷p·b=0

锟斤拷锟斤拷锟斤拷a锟斤拷b锟斤拷锟缴癸拷锟斤拷锟斤拷锟斤拷锟斤拷锟斤拷锟斤拷锟斤拷锟斤拷知锟斤拷锟斤拷一锟斤拷(sh锟斤拷)锟斤拷(sh锟斤拷)k使锟斤拷a=kb

锟斤拷锟斤拷锟斤拷么p·a=p·kb=kp·b=0

锟斤拷锟斤拷锟斤拷a⊥p

锟斤拷锟斤拷∴a锟斤拷α

锟斤拷锟斤拷锟斤拷锟斤拷2

锟斤拷锟斤拷平锟斤拷锟斤拷一锟絣直锟斤拷锟絚锟斤拷平锟斤拷拇锟斤拷锟斤拷锟街�锟斤拷锟絫锟紷锟絣直锟斤拷锟絚锟斤拷平锟斤拷平锟斤拷 [2] 锟斤拷

锟斤拷锟斤拷锟斤拷知锟斤拷a⊥b锟斤拷b⊥α锟斤拷锟斤拷a锟斤拷锟斤拷α锟斤拷锟斤拷锟斤拷锟紺锟斤拷a锟斤拷α

锟斤拷锟斤拷锟紺锟斤拷锟斤拷锟絆(sh锟斤拷)a锟絚b锟侥达拷锟斤拷锟紸锟斤拷b锟絚α锟侥达拷锟斤拷锟紹锟斤拷

锟斤拷锟斤拷锟斤拷锟絆(sh锟斤拷)a锟絚α锟斤拷平锟斤拷锟斤拷锟斤拷么锟斤拷锟斤拷锟洁交锟斤拷锟絆(sh锟斤拷)a∩α=C锟斤拷锟紹锟斤拷BC锟斤拷锟节诧拷锟斤拷直锟斤拷锟较碉拷锟斤拷锟斤拷(g锟斤拷)锟絚(di锟斤拷n)锟絖锟斤拷一锟斤拷(g锟斤拷)平锟斤拷锟斤拷锟斤拷锟紸BC锟斤拷尾锟斤拷锟紹锟矫碉拷锟斤拷ABC

锟斤拷锟斤拷锟斤拷B∈α锟斤拷C∈α锟斤拷b⊥α

锟斤拷锟斤拷∴b⊥BC锟斤拷锟斤拷∠ABC=90°

锟斤拷锟斤拷锟斤拷a⊥b锟斤拷锟斤拷∠BAC=90°

锟斤拷锟斤拷∴锟节★拷ABC锟斤拷锟斤拷锟叫兩傦拷(g锟斤拷)锟斤拷(n锟斤拷i)锟角烇拷90°锟斤拷锟紷锟角诧拷锟斤拷锟杰碉拷锟斤拷锟介。

锟斤拷锟斤拷∴锟斤拷锟絆(sh锟斤拷)锟斤拷锟斤拷锟斤拷锟斤拷a锟斤拷α

锟斤拷锟铰高匡拷锟結訊锟斤拷锟竭匡拷锟斤拷锟斤拷锟斤拷锟斤拷前锟斤拷(zh锟斤拷n)锟戒、志愿锟斤拷锟�(b锟斤拷o)锟斤拷锟饺★拷锟�?j锟斤拷n)?sh锟斤拷)锟斤拷锟斤拷

锟斤拷锟斤拷锟竭匡拷锟絩(sh锟斤拷)锟絞锟斤拷锟斤拷全锟斤拷锟斤拷要锟斤拷(ji锟斤拷)锟絚(di锟斤拷n)

锟斤拷锟斤拷锟組锟斤拷"锟竭匡拷锟絎(w锟斤拷ng)"微锟脚癸拷锟斤拷號(h锟斤拷o)