Предмет: Геометрия, автор: adorofeev2000

AB и CD. -два взаимно перпендикулярных диаметра окружности. Хорда CB продолжена за точку B на отрезок BE, равный CB. Каково взаимоположние прямой DE и окружности ?

adorofeev2000: на помощь

Ответы

Автор ответа: oganesbagoyan
30
DE  касательная т.к.  O  центр окружности .
CO =OD  и  CB = BE(  по условию),значит 
 OB  средняя линия в треугвольнике CDE 
OB || DE  (AB || DE)   ;  <(AB ,CD) =90 °  ⇒<( DE ,CD =90°   ,а CD диаметр.
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