Formula for the Area of a Triangle

To investigate why the Area of a triangle is (base x height.)

  • The parallelogram is decomposed into two triangles. Move the slider from the right position to the left.​
  • Compare the area of the original figure to that of the final figure.


Explore the Area of Triangles.

  • Move points A, B, and C. ​
  • Observe the length of the base and height. ​
  • Observe the area of the triangle.
  1. What do you observe when you keep the base horizontal and slide point A left or right? ​
  2. Does the area agree with your visual count of the squares inside the triangle?

Andre drew a line connecting two opposite corners of a parallelogram. Select all true statements about the triangles created by the line Andre drew.

Here below is a right triangle.