Geometry

Triangle Types and Properties

By SC Editorial 2026-06-04 7 min read

Triangles classify by sides (equilateral, isosceles, scalene) and angles (acute, right, obtuse). Each type has unique properties useful in geometry proofs and real-world design.

Area Formulas

Area = 0.5 * base * height for any triangle. For a right triangle, the legs serve as base and height. Use the Triangle Calculator.

Angle Sum

Interior angles always sum to 180 degrees. In an equilateral triangle, each angle is 60 degrees.

Triangle Inequality

Any side must be less than the sum of the other two. This determines whether three lengths can form a triangle.

Going Deeper

Equilateral, isosceles, scalene, and right triangles - properties and formulas. This guide connects theory to practice — use the related calculators linked at the bottom to verify each example with your own numbers.

Practical Tips

  • Write down given values and unknowns before opening the calculator.
  • Check units and rounding rules appropriate to your context (class, lab, or business).
  • Compare manual working with the calculator result to build confidence.

Common Mistakes to Avoid

  • Rushing inputs without reading field labels carefully.
  • Confusing similar formulas that use different variables or units.
  • Reporting results with more precision than your inputs justify.
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