Mark M. answered 07/18/19
Tutor
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Retired Math prof with teaching and tutoring experience in trig.
y = [sin(7x)]x
lny = xln[sin(7x)]
y' / y = ln[sin(7x)] + 7xcos(7x) / sin(7x)
y' / y = ln[sin(7x)] + 7xcot(7x)
y' = [sin(7x)]x [ ln(sin(7x)) + 7xcot(7x)]