What is the law of cosines?

c² = a² + b² - 2ab·cos(C). It relates two sides and the included angle to the third side.

How do I find angle C from three sides?

Select 'Find angle C' and enter a, b, c. Then cos(C) = (a² + b² - c²) / (2ab).

Given two sides a, b and included angle C (degrees): find side c. Or given three sides: find angle C.

Two sides a, b + angle C → side cThree sides a, b, c → angle C

Side a

Side b

Angle C (degrees)

What is the law of cosines?: c² = a² + b² - 2ab·cos(C). It relates two sides and the included angle to the third side.
How do I find angle C from three sides?: Select 'Find angle C' and enter a, b, c. Then cos(C) = (a² + b² - c²) / (2ab).

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