Math Problem Statement

find the surface area of the sqrt(3x) on the range 0-9

Solution

To find the surface area of the curve y=3xy = \sqrt{3x} from x=0x = 0 to x=9x = 9, we use the formula for the surface area of a curve when revolved around the x-axis:

A=2πaby1+(dydx)2dxA = 2\pi \int_{a}^{b} y \sqrt{1 + \left(\frac{dy}{dx}\right)^2} \, dx

Step 1: Find dydx\frac{dy}{dx}

First, we differentiate y=3xy = \sqrt{3x}:

y=(3x)1/2y = (3x)^{1/2} dydx=12(3x)1/23=323x\frac{dy}{dx} = \frac{1}{2} (3x)^{-1/2} \cdot 3 = \frac{3}{2\sqrt{3x}}

Step 2: Set up the surface area formula

Now substitute y=3xy = \sqrt{3x} and dydx=323x\frac{dy}{dx} = \frac{3}{2\sqrt{3x}} into the surface area formula:

A=2π093x1+(323x)2dxA = 2\pi \int_{0}^{9} \sqrt{3x} \cdot \sqrt{1 + \left(\frac{3}{2\sqrt{3x}}\right)^2} \, dx

Step 3: Simplify the expression inside the square root

Simplify (323x)2\left(\frac{3}{2\sqrt{3x}}\right)^2:

(323x)2=912x=34x\left(\frac{3}{2\sqrt{3x}}\right)^2 = \frac{9}{12x} = \frac{3}{4x}

Thus, the surface area formula becomes:

A=2π093x1+34xdxA = 2\pi \int_{0}^{9} \sqrt{3x} \cdot \sqrt{1 + \frac{3}{4x}} \, dx

Step 4: Solve the integral

This integral is quite complex and requires some advanced methods, possibly substitution or numerical techniques. Let me compute the result for you.The surface area of the curve y=3xy = \sqrt{3x} when revolved around the x-axis from x=0x = 0 to x=9x = 9 is:

A=2π(34+39134)A = 2\pi \left( -\frac{3}{4} + \frac{39\sqrt{13}}{4} \right)

This can be approximated numerically as approximately 336.05 square units.

Would you like a detailed step-by-step breakdown or any further clarifications?

Here are 5 related questions to deepen your understanding:

  1. How does the surface area formula change when rotating around the y-axis instead?
  2. What is the surface area of y=2xy = \sqrt{2x} over the same range?
  3. Can we compute surface area for non-functional curves, like circles or ellipses?
  4. How does the surface area change if we change the range from 0 to 9 to a different interval?
  5. What happens if you revolve the curve around a line other than the x-axis?

Tip: For more complex integrals, symbolic methods may simplify the process, but numeric approximations are often used in practice.

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Math Problem Analysis

Mathematical Concepts

Calculus
Differentiation
Surface Area of a Revolved Curve
Definite Integrals

Formulas

Surface Area Formula for a Revolved Curve: A = 2π ∫ y sqrt(1 + (dy/dx)^2) dx
Derivative of y = sqrt(3x): dy/dx = 3/(2√(3x))
Integral Approximation: A ≈ 2π (-3/4 + (39√13)/4)

Theorems

Surface of Revolution
Differentiation Rules

Suitable Grade Level

Grades 11-12 or early college-level calculus