Math Problem Statement

Evaluate the double integral \( \int_0^1 \int_x^3 e^{x^2} \, dy \, dx \).

Solution

The integral in the image is a double integral:

01x3ex2dydx\int_0^1 \int_{x}^{3} e^{x^2} \, dy \, dx

Step-by-Step Solution:

Step 1: Evaluate the inner integral

The inner integral is with respect to yy, treating xx as a constant: x3ex2dy\int_x^3 e^{x^2} \, dy

Since ex2e^{x^2} does not depend on yy, it is treated as a constant during the integration: x3ex2dy=ex2x31dy=ex2[y]x3\int_x^3 e^{x^2} \, dy = e^{x^2} \int_x^3 1 \, dy = e^{x^2} \cdot \left[ y \right]_x^3

Substituting the limits of yy: ex2[y]x3=ex2(3x)e^{x^2} \cdot \left[ y \right]_x^3 = e^{x^2} \cdot \left(3 - x\right)

So the result of the inner integral is: ex2(3x)e^{x^2} \cdot (3 - x)

Step 2: Evaluate the outer integral

The outer integral is: 01ex2(3x)dx\int_0^1 e^{x^2} \cdot (3 - x) \, dx

Distribute ex2e^{x^2}: 01[3ex2xex2]dx\int_0^1 \left[ 3e^{x^2} - x e^{x^2} \right] \, dx

This can be separated into two integrals: 013ex2dx01xex2dx\int_0^1 3e^{x^2} \, dx - \int_0^1 x e^{x^2} \, dx

Step 3: Solve each part

  1. For 013ex2dx\int_0^1 3e^{x^2} \, dx:
    This integral does not have a closed-form solution and must be left as is or evaluated numerically.

    013ex2dx(numerical evaluation needed if exact value is required)\int_0^1 3e^{x^2} \, dx \quad (\text{numerical evaluation needed if exact value is required})

  2. For 01xex2dx\int_0^1 x e^{x^2} \, dx:
    Let u=x2u = x^2, so du=2xdxdu = 2x \, dx or 12du=xdx\frac{1}{2} du = x \, dx.
    When x=0x = 0, u=0u = 0.
    When x=1x = 1, u=1u = 1.
    Substituting into the integral: 01xex2dx=1201eudu\int_0^1 x e^{x^2} \, dx = \frac{1}{2} \int_0^1 e^u \, du

    The integral of eue^u is simply eue^u: 1201eudu=12[eu]01=12(e1e0)=12(e1)\frac{1}{2} \int_0^1 e^u \, du = \frac{1}{2} \left[ e^u \right]_0^1 = \frac{1}{2} \left( e^1 - e^0 \right) = \frac{1}{2} (e - 1)

Step 4: Combine the results

The final result is: 01x3ex2dydx=301ex2dx12(e1)\int_0^1 \int_x^3 e^{x^2} \, dy \, dx = 3 \int_0^1 e^{x^2} \, dx - \frac{1}{2} (e - 1)

Final Answer

01x3ex2dydx=301ex2dx12(e1)\boxed{\int_0^1 \int_x^3 e^{x^2} \, dy \, dx = 3 \int_0^1 e^{x^2} \, dx - \frac{1}{2} (e - 1)}

Would you like a numerical approximation for the result or further explanation on any step?


Follow-up Questions:

  1. What is the numerical approximation for 01x3ex2dydx\int_0^1 \int_x^3 e^{x^2} \, dy \, dx?
  2. How is substitution used in integrals involving exponential functions?
  3. Why does 01ex2dx\int_0^1 e^{x^2} \, dx lack a closed-form solution?
  4. What are some techniques for solving double integrals?
  5. How would the bounds change the approach if reversed?

Tip:

For integrals involving ex2e^{x^2}, numerical methods like Simpson's rule or Gaussian quadrature are often necessary for practical evaluations.

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Math Problem Analysis

Mathematical Concepts

Double Integration
Exponential Functions
Change of Variables
Numerical Integration

Formulas

Integral of \( e^{u} \): \( \int e^u \, du = e^u + C \)
Change of variables: \( u = x^2 \), \( du = 2x \, dx \)

Theorems

Fubini's Theorem

Suitable Grade Level

Undergraduate (Calculus II/III)