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Law of Cosines Calculator

Solve any triangle — find missing sides or angles using the Law of Cosines and Sines. Get area, perimeter, triangle type, visual diagram, and full step-by-step derivation.

c² = a² + b² − 2ab·cos(C) • Supports SSS, SAS, SSA, AAS, ASA modes

Triangle Inputs

Enter any 3 known values — sides a, b, c and angles A, B, C (in degrees)

Known Information

Side a

opposite to angle A

Side b

opposite to angle B

Side c

opposite to angle C

Angle A (°)

opposite to side a

Angle B (°)

opposite to side b

Angle C (°)

opposite to side c

Quick Presets

Triangle Summary

—

Triangle Type

Area—

Perimeter—

Semi-perimeter (s)—

Sides

a—

b—

c—

Angles

A—

B—

C—

Circle Radii

Circumradius (R)—

Inradius (r)—

Law of Cosines Calculator

Triangle Inputs

Step-by-Step Solution

Complete Triangle Solution

Formulas Applied