The number of square units it takes to exactly fill the interior of a
triangle.
Try this 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.
where
b is the length of the
base
a is the length of the corresponding
altitude
You can choose any side to be the
base.
It need not be the one drawn at the bottom of the triangle.
The altitude
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.
Calculator
Use the calculator on the right to calculate the area of a triangle
Enter any two values and the other will be calculated.
For example: enter the base and altitude and press 'Calculate'. The area will be calculated.
Similarly, if you enter the area and base, the altitude needed to get that area will be calculated.
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 sidetoside.
Therefore, all the triangles you can create this way have the same area.
Other triangle topics
General
Perimeter / Area
Triangle types
Triangle centers
Congruence and Similarity
Solving triangles
Triangle quizzes and exercises
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