The number of square units it takes to exactly fill the interior of a
Drag the orange dots on each vertex
to reshape the triangle. The formula shown will recalculate the area using this method.
Most common method
Usually called "half of base times height", the area of a triangle is given by the formula below.
b is the length of the
a is the length of the corresponding
You can choose any side to be the
It need not be the one drawn at the bottom of the triangle.
must be the one corresponding to the base you choose.
The altitude is the line perpendicular to the selected base from the opposite vertex.
In the figure above, one side has been chosen as the base and its corresponding altitude is shown.
Methods for finding triangle area
Things to try
In the figure above, click on "freeze altitude".
As you now drag point A, notice that the area does not change.
The area is dependent on the base and height, and neither of them changes as you move the top vertex side-to-side.
Therefore, all the triangles you can create this way have the same area.
Related triangle topics
Perimeter / Area
Congruence and Similarity
Triangle quizzes and exercises
(C) 2009 Copyright Math Open Reference. All rights reserved