It was first explained in Sections 12 and 13 of Book II of Euclid's Elements and is incorporated in the definition of the dot product.
It was first explained in Sections 12 and 13 of Book II of Euclid's Elements and is incorporated in the definition of the dot product. It can be used to compute any angle of a given triangle if all three sides are known or the 3rd side of a triangle if two sides and the enclosed angle are known. The Pythagorean theorem is a generalization of it when big C is ninety degrees. The law states that little c squared equals little a squared plus little b squared minus two times little a times little b times the cosine of C. FTP identify this law which can be used with the Law of Sines to find all sides and angles of a triangle.
It was first explained in Sections 12 and 13 of Book II of Euclid's Elements and is incorporated in the definition of the dot product.
Law of {Cosines} or {Cosine} Law or {Cosine} Rule.