data-ad-format="horizontal">



 
Altitude

1. An altitude of a triangle

An altitude is a line which passes through a vertex of a triangle, and meets the opposite side at right angles. A triangle has three altitudes. For more see Altitudes of a triangle.

An interesting fact is that the three altitudes always pass through a common point called the orthocenter of the triangle. See Orthocenter of a triangle

2. Quadrilaterals with a pair of parallel sides

If a quadrilateral has a pair of parallel sides, both of them are called a base. Base and altitude of a parallelogram In a similar way to triangles, the altitude of such a figure is the perpendicular distance from a base to the opposite side. Since they are parallel, either one will do.

Note: A common mistake is to use the length of the slanted side as the altitude. This is wrong. You must use the vertical distance as shown.

Pages referring to 'altitude'

The altitude of a triangle is the perpendicular from a vertex to the opposite side.
The conventional method of calculating the area of a triangle (half base times altitude) with pointers to other methods and special formula for equilateral triangles
This page shows how to construct one of the three altitudes of a triangle, using only a compass and straightedge or ruler. A Euclidean construction.
This page shows how to construct one of the three altitudes of an obtuse triangle, using only a compass and straightedge or ruler. A Euclidean construction.
Definiton and properties of a trapezoid (coordinate geometry) including altitude and median
Definition and properties of triangles