prove cos^2(x)-sin^2(x)=cos(2x)

I just need to understand how these two equal each other. There must be an identity I can use somewhere. Please show step by step how they equal each other! Thank you!
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1 Answer

cos(A+B)=cosA.cosB-sinA.sinB

cos(x+x)=cosx.cosx-sinx.sinx

cos(2x)=cos^2(x)-sin^2(x)
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