cosines law

Cosines Law.  Let $a$, $b$, $c$ be the sides of a triangle and $A$ the angle opposite to $a$. Then

$$a^2=b^2+c^2-2bc\cos A.$$

Remark.  Cosines law is the generalised form of Pythagorean theorem, which latter concerns only the right triangles.

Title	cosines law
Canonical name	CosinesLaw
Date of creation	2013-03-22 11:42:35
Last modified on	2013-03-22 11:42:35
Owner	drini (3)
Last modified by	drini (3)
Numerical id	26
Author	drini (3)
Entry type	Theorem
Classification	msc 51M04
Classification	msc 05A15
Classification	msc 05A10
Classification	msc 05A16
Synonym	law of cosines
Related topic	SinesLaw
Related topic	PythagorasTheorem
Related topic	DerivationOfCosinesLaw
Related topic	CosinesLaw
Related topic	StewartsTheorem
Related topic	AlternativeProofOfTheSinesLaw
Related topic	SinesLawProof
Related topic	ProofOfStewartsTheorem