How to find areas of triangles using the formula: A = ˝base×height.
The base and perpendicular height of a triangle can be identified as follows:
Any side can be the base, and then the perpendicular height extends from the vertex opposite the base to meet the base at a 90° angle.
For a right angled triangle, the perpendicular height can be one of the sides:
For an obtuse angled triangle (that is, a triangle with an angle greater than 90°) the perpendicular height may lie outside of the triangle itself:
If you know the base and perpendicular height of a triangle, then you can find the area using this formula:
Maths Helper Plus can show the
calculations and also draw a diagram for calculating the area of a triangle
given the base and perpendicular height.
Step 2 Display the parameters box
Press the F5 key to display the parameters box:
Click on the 'A' edit box with the mouse, then type the perpendicular height of your triangle.
Similarly, click on the 'B' edit box and type the value of the base.
Click the 'Update' button to refresh the diagram and calculations.
Step 3 Adjust the shape of the triangle diagram
NOTE: The following procedure does not effect the calculations in any way because the base and perpendicular height remain the same.
If you know the shape of the triangle (eg if you have been given a diagram) then you can adjust the shape of the triangle in Maths Helper Plus to look like your triangle.
The 'C' value in the parameters box is the distance of the top vertex of the triangle from the left side of the base. For example...
Step 4 Adjust the scale of the labelled diagram
If the labelled diagram does not display the points, the scale needs to be reduced. In this case, briefly press the F10 key enough times until the two plotted points are seen.
You can make the diagram bigger by holding down 'Ctrl' while you press F10.