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Law of Cosines Calculator

Solve any triangle using the Law of Cosines: c² = a² + b² − 2ab·cos(C). Handles SAS (find side) and SSS (find angles) configurations.

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The Law of Cosines: c² = a² + b² − 2ab·cos(C). Solves any triangle given SSS or SAS.

Características PrincipalesLaw of Cosines Calculator

SAS: find missing side given 2 sides + included angle
SSS: find all angles given 3 sides
Area calculation (SAS and Heron's formula)
Full triangle solution
Triangle inequality validation

Por Qué Usar Esta HerramientaLaw of Cosines Calculator

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Usa en cualquier dispositivo — escritorio, tablet o teléfono. Sin descargas necesarias.

Preguntas FrecuentesLaw of Cosines Calculator

What is the Law of Cosines?
The Law of Cosines: c² = a² + b² − 2ab·cos(C). It generalizes the Pythagorean theorem to any triangle (when C=90°, cos(90°)=0 and it reduces to c²=a²+b²). Use it when you know two sides and the included angle (SAS) to find the third side, or all three sides (SSS) to find any angle.
How do I find an angle using the Law of Cosines?
Rearranging: cos(C) = (a² + b² − c²) / (2ab). To find angle C, take the inverse cosine: C = arccos((a² + b² − c²) / (2ab)). Similarly for angles A and B. This works for any triangle — you just need all three side lengths.
What is the difference between Law of Sines and Cosines?
Law of Cosines: use for SSS (3 sides) or SAS (2 sides + included angle). It is more robust and avoids the ambiguous case. Law of Sines: use for ASA or AAS (2 angles + a side). Both methods give the same answer when multiple approaches work — choose whichever fits the given information.

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Law of Cosines Calculator - Herramienta Gratuita en Línea | WebToolsMagic