How to Find Altitude in Geometry

The altitude of a triangle is the imaginary line between each vertex and its opposite side.

The altitude of a triangle is essentially the height, measured at a 90-degree angle from one side. Knowing the altitude allows you to calculate the area of the triangle or perform trigonometric calculations of angles and sides. There are three altitudes on every triangle. These altitudes constitute the distance from each point, or vertex, of the triangle to its opposite side.

Things You'll Need

• Ruler
• Protractor
• Pencil

Instructions

1. Locate the side opposite the vertex for which you wish to find the altitude.

2. Place a protractor along this side and slide it sideways until the 90-degree mark aligns with the opposite vertex.

3. Place a mark exactly where the center mark of the protractor points to the side of the triangle.

4. Measure the distance from this mark to the opposite vertex. This will be the length of the altitude.

References

• Home School Math: Altitude of a Triangle
• Cliff Notes: Altitudes, Medians, and Angle Bisectors