Basic Rules of Triangles
There are some rules that are true for all the different kinds of triangles. Below are the four most important rules. Note: The triangles in the figures represent any triangle.
- The sum of the interior angles of a triangle is 180°.
x° + y° + z° = 180°
- The length of the longest side of a triangle must be less than the sum of the lengths of the other two sides of the triangle, but greater than the difference of the lengths.
(AB – BC) < AC < (AB + BC)
- The longest side of a triangle is opposite the largest angle and the shortest side is opposite the smallest angle.
∠B is the largest angle so AC is the longest side.
AB is the shortest side so ∠C is the smallest angle.
- If you extend one side of the triangle, the exterior angle formed will be equal to the sum of the other two interior angles in the triangle.
x° + z° = n°