The Law of Cosines - Yet Another PWW

John Molokach got a featured proof without words in The American Mathematical Monthly (Vol. 121, No. 8, October 2014):

John Molokach's proof of the Cosine Law

$a=b\cos C+c\cos B\\ b=c\cos A+a\cos C\\ c=a\cos B+b\cos A\\ c^{2}=ac\cos B+bc\cos A\\ c^{2}=a(a-b\cos C)+b(b-a\cos C)\\ c^{2}=a^{2}-2ab\cos C+b^{2}.$

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