In Euclidean geometry, a plane is defined by:
- three non-collinear points
- a line and a point not on the line
- two intersecting lines
- two parallel lines
A line can intersect a plane in a single point, or it can be in the plane.
Two planes perpendicular to the same line are parallel to eachother.
Two lines perpendicular to the same plane are parallel to eachother.
Two planes can be parallel, or they can intersect in a line.
If two lines are perpendicular to eachother and one of them is in a plane, the other is perpendicular to the plane.
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