A triangle is a three-sided, two-dimensional shape. Triangles and their angles form the basis of most basic geometric calculations. However, learning how to bisect a triangle -- or divide it into two parts of equal area -- doesn't require any mathematical formula or difficult calculation. You don't even need to know its area to chop it in half. While there are more complex ways to divide a triangle into two equal parts, this guide will focus on the simplest.
To calculate the area of the triangle, multiply the base (the line you measured) by the height (the line you drew), then divide the result by 2.
Measure one side of the triangle. It doesn't matter which side you pick.
Mark the midpoint of that side. To find the midpoint, divide the length of the side by 2, then measure to that distance. For example, if the side you chose is 6 inches long, divide 6 by 2. When you dived 6 by 2, you get 3, so the midpoint of the side will be 3 inches from either end. Measure 3 inches from one end of the side, and mark that point.
Draw a line from the opposite angle to the midpoint mark you just made. Draw along your ruler to make the line straight. You have just bisected the triangle. Even though you never calculated the area of the triangle, the area on each side of your line will be the same.
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