Activity on the Base & Height of a Triangle

Triangles are shapes that have three straight sides.

Triangles are a kind of minimum object. Objects with less than three sides are not polygons--they do not enclose space. It is also the only polygon that has generated its own branch of mathematics--trigonometry.

Bases

Triangles have three bases. One of the first activities that students should see is that triangles look different when each of the three sides are placed down--selected as the base. Have the students do this with equilateral triangles, right triangles and obtuse triangles.

Heights

A necessary activity for understanding triangles is to locate the height when each of the three sides of the triangle is selected as the base. Triangles are often classified as: acute, when all angles are less than 90 degrees; right, when one angle is 90 degrees; and obtuse, when one angle is greater than 90 degrees. For each class, have the students describe how the height changes as different bases are chosen.

Parallelograms

If a triangle is duplicated, the two triangles can be fitted together to make a parallelogram. Look at how different types of triangles can be duplicated and assembled to what kind of parallelogram. For example, a right triangle will produce a rectangle. Note what happens to the base and heights during this process.

References

• MathIsFun: Triangles
• Math: Triangles
• OnLineMathLearning: Types of Triangles

Resources

• Read this Article in Spanish
• MathWorld: Triangle