What the tool does, how to run it, and what to expect from the result.
Three sides fix a triangle. The law of cosines gives each angle, Heron’s formula gives the area, and the largest angle tells you whether it is acute, right or obtuse. Sides 7, 8 and 9 give angles of 48.19°, 58.41° and 73.40° and an area of 26.83. Three lengths only make a triangle if each is shorter than the other two combined.
A quick way to understand who this helps, what it solves, and where it connects next.
Students, teachers and anyone checking a calculation.
Using the triangle calculator without installing anything or signing up.
Short answers for the questions people usually have before trying a utility like this.
Area = √(s(s − a)(s − b)(s − c)), where s is half the perimeter. For 3, 4, 5: s = 6 and the area is √36 = 6.
The triangle inequality: each side must be less than the sum of the other two. 1, 2 and 5 cannot close.
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Enter your numbers and the result updates live in your browser. Nothing is uploaded and no server is used.
Calculations run locally in your browser; nothing is uploaded.