Derivative of the product of a sine and a cosine: ![]()
Via the Scalar Multiple rule, we can treat this as
.
We can go a step further and consider it as involving a product and apply the Product rule
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Using the derivative of the sine and cosine, we get
![]()
Simplifying and reordering, we get
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Note that the arguments in the result are the same as the arguments in the original problem.