Constructing a Triangle with 3 Known Sides
If we know the lengths of a triangle's 3 sides, we can draw the triangle using a ruler and drafting compass.
It is fun and easy to do.
In this example we are told the triangle has sides of 23, 17 and 12 (press the play button):
images/construct.js?mode=tri3sides
Note: this isn't a classic construction as we measured using a ruler, but it is still a perfectly good method.
Will Any 3 Side Lengths Work?
Any side of a triangle must be shorter than the other two sides added together.
Why? Imagine one side is not shorter:
- If a side is longer than the other two sides there's a gap:
- If a side is equal to the other two sides it isn't a triangle (just a straight line back and forth).
Learn more at Triangle Inequality Theorem.
SSS
Knowing the three sides is also called "SSS" (meaning "Side, Side, Side"). Learn more at Solving SSS Triangles.