Math Problem Statement

Evaluate the integral ∫ e^x sin(x) dx.

Solution

The integral shown in the image is:

exsin(x)dx\int e^x \sin(x) \, dx

This integral can be solved using the method of integration by parts. Let’s solve it step by step:

Step 1: Recall Integration by Parts Formula

udv=uvvdu\int u \, dv = u v - \int v \, du

Step 2: Select uu and dvdv

Let:

  • u=sin(x)u = \sin(x) (so that du=cos(x)dxdu = \cos(x) \, dx)
  • dv=exdxdv = e^x \, dx (so that v=exv = e^x, since exdx=ex\int e^x \, dx = e^x)

Step 3: Apply Integration by Parts

exsin(x)dx=exsin(x)excos(x)dx\int e^x \sin(x) \, dx = e^x \sin(x) - \int e^x \cos(x) \, dx

Step 4: Solve the Remaining Integral

Now, we need to compute excos(x)dx\int e^x \cos(x) \, dx. Use integration by parts again:

  • Let u=cos(x)u = \cos(x) (so that du=sin(x)dxdu = -\sin(x) \, dx)
  • Let dv=exdxdv = e^x \, dx (so that v=exv = e^x)

excos(x)dx=excos(x)ex(sin(x))dx\int e^x \cos(x) \, dx = e^x \cos(x) - \int e^x (-\sin(x)) \, dx excos(x)dx=excos(x)+exsin(x)dx\int e^x \cos(x) \, dx = e^x \cos(x) + \int e^x \sin(x) \, dx

Step 5: Solve for the Original Integral

Let I=exsin(x)dxI = \int e^x \sin(x) \, dx. Substituting the result above, we have: I=exsin(x)(excos(x)+I)I = e^x \sin(x) - \left( e^x \cos(x) + I \right) I=exsin(x)excos(x)II = e^x \sin(x) - e^x \cos(x) - I 2I=exsin(x)excos(x)2I = e^x \sin(x) - e^x \cos(x) I=12(exsin(x)excos(x))I = \frac{1}{2} \left( e^x \sin(x) - e^x \cos(x) \right)

Final Answer:

exsin(x)dx=12(exsin(x)excos(x))+C\int e^x \sin(x) \, dx = \frac{1}{2} \left( e^x \sin(x) - e^x \cos(x) \right) + C

Where CC is the constant of integration.

Would you like further details or explanations on any of the steps?


Related Questions:

  1. How does the choice of uu and dvdv affect integration by parts?
  2. Can this integral be solved using another method, such as substitution?
  3. How does this solution extend to integrals of excos(x)e^x \cos(x)?
  4. What is the intuition behind using integration by parts for this problem?
  5. How would the solution change if the integral were exsin(x)dx\int e^{-x} \sin(x) \, dx?

Tip:

When solving oscillatory integrals involving exe^x with trigonometric functions, expect to use integration by parts multiple times and solve for the original integral algebraically.

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Math Problem Analysis

Mathematical Concepts

Integration
Integration by Parts
Algebraic Manipulation

Formulas

Integration by Parts: ∫ u dv = uv - ∫ v du

Theorems

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Suitable Grade Level

Undergraduate Mathematics (Calculus)