calc
posted by Adam .
f(x)=8cos4x
What is the derivative? Im doing online homework and i keep getting an incorrect answer. How do you work out this problem correctly? thanks

you must know that if
y = a cos kx, where k is a constant, then
dy/dx = a(k)sin kx
so f(x) = 8cos 4x
f'(x) = 32sin 4x
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