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Proof: cos(a+b) = (cos a)(cos b)-(sin a)(sin b)

Proof of the trig identity: cos(a+b) = (cos a)(cos b)-(sin a)(sin b)

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Proof: cos(a+b) = (cos a)(cos b)-(sin a)(sin b)

Proof of the trig identity: cos(a+b) = (cos a)(cos b)-(sin a)(sin b)