Reciprocele teoremei celor trei perpendiculare

Reciproca 1:

$$\begin{gathered} \overline{)CO\perp \alpha \\ CA\perp b \\ OA, b\subset \alpha } \Rightarrow OA\perp b \end{gathered}$$

 

Reciproca 2:

$$\begin{gathered} \overline{)OA, b\subset \alpha \\ OA\perp b \\ CA\not\subset \alpha \\ CA\perp b \\ CO\perp OA} \Rightarrow CO\perp \alpha . \end{gathered}$$