Предмет: Геометрия, автор: twentyonepeople08

Прямая DА перпендикулярна сторонам АВ и АС треугольника АВС и не лежит в его плоскости. Перпендикулярными являются плоскости
1. DАВ и DВС
2. DАС и DВС
3. DАС и АВС
4. DВС и АВС

Ответы

Автор ответа: siestarjoki

Если прямая перпендикулярна двум пересекающимся прямым в плоскости, то она перпендикулярна плоскости.

DА⊥АВ, DА⊥АС => DА⊥(АВС)

Если плоскость проходит через перпендикуляр к другой плоскости, то она перпендикулярна этой плоскости.

DА⊥(АВС) => (DАС)⊥(АВС)

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