Chapter 10: Problem 72
When \(a\) and \(b\) are real, we define \(e^{(a+i b) x}\) with the equation $$ e^{(a+i b) x}=e^{a x} \cdot e^{i b x}=e^{a x}(\cos b x+i \sin b x) $$ Differentiate the right-hand side of this equation to show that $$ \frac{d}{d x} e^{(a+i b) x}=(a+i b) e^{(a+i b) x} $$ Thus the familiar rule \((d / d x) e^{k x}=k e^{k x}\) holds for \(k\) complex as well as real.
Short Answer
Step by step solution
Differentiate the term involving \(e^{a x}\)
Differentiate the trigonometric terms
Apply the Product Rule
Calculate both terms from the product rule
Combine and simplify
Conclusion
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Complex Exponentials
- The real exponential component: \( e^{ax} \).
- The trigonometric component: \( e^{ibx} = \cos(bx) + i\sin(bx) \).
Chain Rule in Calculus
- \( h'(x) = f'(g(x)) \cdot g'(x) \).
Product Rule in Calculus
- \( y'(x) = u'(x)\cdot v(x) + u(x)\cdot v'(x) \).