(5-2)+Law+of+Cosines)

The wonderful Law of Cosines!

The **law of cosines** gives a formula for the square of any side of an oblique triangle in terms of the other two sides and their included angle.

If triangle ABC is an oblique triangle with sides a, b, c, and angles alpha, beta, gamma, then a²=b²+c²-2bc(cos(alpha)) b²=a²+c²-2ac(cos(beta)) c²=a²+b²-2ab(cos(gamma)) [|Videooo!]

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