Write cos3x+cos4x as a product of trigonometric functions?
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Originally Posted by derek1008 Write cos3x+cos4x as a product of trigonometric functions? one of the sum to product identities ... $\displaystyle \cos{A} + \cos{B} = 2\cos\left(\frac{A+B}{2}\right)\cos\left(\frac{A-B}{2}\right)$
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