Linked from

The 15 pages that link to Perpendicular lines, each with the reason it gives.

• Right triangleRelated: The legs meet perpendicularly at the triangle’s right-angle vertex.

• Perpendicular bisectorCompared with: It guarantees a right angle but need not pass through the segment’s midpoint.

• Parallel linesCompared with: They provide the contrasting case of intersecting lines with a fixed angle.

• OrthocenterNarrower topic: An altitude is defined by perpendicularity to the opposite side’s line.

• Angle bisectorCompared with: An angle bisector need not meet either side at a right angle.

• Geometric constructionRelated: Constructing perpendiculars is a basic task built from straightedge-and-compass operations.

• Thales' theoremRelated: The theorem guarantees the two chords at the vertex are perpendicular.

• Radical axisRelated: The radical axis is perpendicular to the line joining the circle centers.

• TransversalRelated: A transversal can meet another line perpendicularly, making every angle at that intersection a right angle.

• Van Aubel's theoremNarrower topic: Perpendicularity is one of the theorem's two conclusions.

• Horizontal line (geometry)Related: A horizontal line is perpendicular to vertical lines in the same coordinate system.

• Perpendicular axis theoremRelated: The two in-plane axes must be perpendicular to each other and to the out-of-plane axis.

• Bottema's theoremRelated: Each of the three constructed lines is perpendicular to a side.

• Droz-Farny line theoremRelated: Their right-angle relation is the theorem’s key condition.

• Inverse Pythagorean theoremRelated: The conclusion is equivalent to the two sides enclosing the tested angle being perpendicular.