Exercise · ZW-COMPLEX-DERIVATIVE-003 · ★☆☆ Basic
Compute \(f'(2)\) for \(f(z)=\dfrac1z\).
Choose one option.
Show answer
- B. \(-\dfrac14\)
Explanation
\(f'(z)=-1/z^2\), so \(f'(2)=-\frac14\). Directly: \(\frac{1/(2+h)-1/2}{h}=\frac{-1}{2(2+h)}\to-\frac14\).
Review the concept: Complex derivative
The derivative \(f'(z_0)\) of a complex function \(f\) at a point \(z_0\) is the limit of the difference quotient as \(z\) approaches \(z_0\) from any direction in the plane, if that limit exists.
\[f'(z_0)=\lim_{z\to z_0}\frac{f(z)-f(z_0)}{z-z_0}\]
More practice problems: complex derivative
- ZW-COMPLEX-DERIVATIVE-001 Compute f'(3) for f(z)=z^2.
- ZW-COMPLEX-DERIVATIVE-002 If f(z)=z^5, what is f'(1)?
- ZW-COMPLEX-DERIVATIVE-004 What is the derivative of e^z at z=0?
- ZW-COMPLEX-DERIVATIVE-005 If f is differentiable at z_0, what follows?
- ZW-COMPLEX-DERIVATIVE-006 Compute f'(1+i) for f(z)=z^3-2z^2+5z.
- ZW-COMPLEX-DERIVATIVE-007 Compute g'(0) for g(z)=z e^z.
- ZW-COMPLEX-DERIVATIVE-008 Compute h'(1) for h(z)=(z^2)/(z+1).
- ZW-COMPLEX-DERIVATIVE-009 For f(z)=bar z at z_0=2, what happens to the difference quotient?