http://www.ck12.org Chapter 10. Perimeter and Area
10.3 Area and Perimeter of Triangles
Here you’ll learn how to calculate the area and perimeter of a triangle and how the area of triangles relates to the
area of parallelograms.
What if you wanted to find the area of a triangle? How does this relate to the area of a parallelogram? After
completing this Concept, you’ll be able to answer questions like these.
Watch This
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/52484CK-12 Foundation: Chapter10AreaandPerimeterofTrianglesA
Learn more about the area of triangles by watching the video at this link.
Guidance
If we take parallelogram and cut it in half, along a diagonal, we would have two congruent triangles. Therefore, the
formula for the area of a triangle is the same as the formula for area of a parallelogram, but cut in half.
Thearea of a triangleisA=^12 bhorA=bh 2. In the case that the triangle is a right triangle, then the height and base
would be the legs of the right triangle. If the triangle is an obtuse triangle, the altitude, or height, could be outside of
the triangle.
Example A
Find the area of the triangle.