Triangle Calculator

Solve any triangle from three sides, or from two sides plus the included angle.

Solution

Area

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Perimeter

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Side c

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Angle A

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Angle B

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Angle C

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Type

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How it works

SSS (three sides) — area comes from Heron's formula, angles from the law of cosines.

s = (a + b + c) / 2 · Area = √(s(s−a)(s−b)(s−c))

SAS (two sides + included angle) — the third side comes from the law of cosines; area is ½·a·b·sin(C).

Triangle inequality

Three sides only form a triangle if each side is shorter than the sum of the other two. Try entering 1, 1, 5 — it won't work.