Apply Chain Rule: Use the chain rule to differentiate f(x)=arctan(3x). The chain rule states that the derivative of a composite function is the derivative of the outer function evaluated at the inner function times the derivative of the inner function.
Derivative of arctan(u): The outer function is arctan(u) with u=3x. The derivative of arctan(u) with respect to u is 1+u21.
Derivative of 3x: The inner function is u=3x. The derivative of 3x with respect to x is 3.
Apply Chain Rule: Apply the chain rule: f′(x)=1+(3x)21⋅dxd(3x).
Calculate Derivative: Calculate the derivative: f′(x)=(1+9x21)⋅3.
Simplify Expression: Simplify the expression: f′(x)=1+9x23.
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