Math Problem Statement

Evaluate the double integral \( \int_0^2 \int_0^{\sqrt{x}} x^3 y \, dy \, dx \)

Solution

The integral in the image is a double integral of the form:

020xx3ydydx\int_0^2 \int_0^{\sqrt{x}} x^3 y \, dy \, dx

Let's evaluate this step by step.

Step 1: Inner Integral with respect to yy

The inner integral is:

0xx3ydy\int_0^{\sqrt{x}} x^3 y \, dy

Since x3x^3 is treated as a constant with respect to yy, we integrate yy alone:

x30xydyx^3 \int_0^{\sqrt{x}} y \, dy

The integral of yy is:

y22\frac{y^2}{2}

So, applying the limits y=0y = 0 to y=xy = \sqrt{x}:

x3[y22]0x=x3((x)22022)=x3(x2)x^3 \left[ \frac{y^2}{2} \right]_0^{\sqrt{x}} = x^3 \left( \frac{(\sqrt{x})^2}{2} - \frac{0^2}{2} \right) = x^3 \left( \frac{x}{2} \right)

Thus, the result of the inner integral is:

x42\frac{x^4}{2}

Step 2: Outer Integral with respect to xx

Now, we need to evaluate the outer integral:

02x42dx\int_0^2 \frac{x^4}{2} \, dx

This simplifies to:

1202x4dx\frac{1}{2} \int_0^2 x^4 \, dx

The integral of x4x^4 is:

x55\frac{x^5}{5}

Applying the limits x=0x = 0 to x=2x = 2:

12[x55]02=12(255055)=12(325)=165\frac{1}{2} \left[ \frac{x^5}{5} \right]_0^2 = \frac{1}{2} \left( \frac{2^5}{5} - \frac{0^5}{5} \right) = \frac{1}{2} \left( \frac{32}{5} \right) = \frac{16}{5}

Final Answer:

The value of the double integral is:

165\boxed{\frac{16}{5}}

Would you like more details on any step or further explanation? Here are some questions to expand your understanding:

  1. How does the order of integration affect the result of a double integral?
  2. Can you change the limits of integration for this problem?
  3. What happens if you reverse the order of integration in this particular case?
  4. How would the problem change if the limits of yy were different?
  5. How is this type of problem used in physical applications like finding volumes?

Tip: When integrating over a region, always check if reversing the order of integration might simplify the process.

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Math Problem Analysis

Mathematical Concepts

Calculus
Double Integrals

Formulas

Integral of y: \( \int y \, dy = \frac{y^2}{2} \)
Integral of x^4: \( \int x^4 \, dx = \frac{x^5}{5} \)

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12 (Advanced Calculus)