Math Problem Statement

Do the following for the given curve on the given interval. Set up an integral for the length of the curve. Graph the curve to see what it looks like. Use your grapher's or computer's integral evaluator to find the curve's length numerically. y = 3sin x - 3x cos x, 0 <= x <= pi

Solution

To solve the problem involving the curve y=3sin(x)3xcos(x)y = 3\sin(x) - 3x\cos(x) over the interval 0xπ0 \leq x \leq \pi, we need to complete the following steps:

(a) Set up an integral for the length of the curve

The formula for the arc length LL of a curve y=f(x)y = f(x) over the interval axba \leq x \leq b is given by:

L=ab1+(dydx)2dxL = \int_a^b \sqrt{1 + \left( \frac{dy}{dx} \right)^2} \, dx

First, we need to compute the derivative dydx\frac{dy}{dx} of the given function y=3sin(x)3xcos(x)y = 3\sin(x) - 3x\cos(x).

dydx=3cos(x)3cos(x)+3xsin(x)\frac{dy}{dx} = 3\cos(x) - 3\cos(x) + 3x\sin(x)

Simplifying:

dydx=3xsin(x)\frac{dy}{dx} = 3x\sin(x)

Now, square the derivative:

(dydx)2=(3xsin(x))2=9x2sin2(x)\left( \frac{dy}{dx} \right)^2 = (3x\sin(x))^2 = 9x^2\sin^2(x)

Thus, the arc length integral becomes:

L=0π1+9x2sin2(x)dxL = \int_0^\pi \sqrt{1 + 9x^2\sin^2(x)} \, dx

(b) Graph the curve to see what it looks like

I will plot the graph of the curve y=3sin(x)3xcos(x)y = 3\sin(x) - 3x\cos(x) over the interval [0,π][0, \pi] to visualize the shape.

(c) Use a grapher's or computer's integral evaluator to find the curve's length numerically

To calculate the length numerically, I'll compute the integral 0π1+9x2sin2(x)dx\int_0^\pi \sqrt{1 + 9x^2\sin^2(x)} \, dx. Let me do this calculation now.The numerical value of the curve's length, calculated using the integral 0π1+9x2sin2(x)dx\int_0^\pi \sqrt{1 + 9x^2\sin^2(x)} \, dx, is approximately 10.3210.32 units.

Would you like a detailed explanation of any of the steps? Here are five related questions you might consider:

  1. How is the formula for the arc length of a curve derived?
  2. Can you explain why we need the derivative of yy to compute the arc length?
  3. How can the arc length formula be applied to curves in parametric form?
  4. What are common methods for numerically solving integrals like this?
  5. How would the arc length formula change for a curve in polar coordinates?

Tip: When calculating arc lengths, always check if the function allows for simplifications in the integrand to make the integral easier to evaluate.

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Math Problem Analysis

Mathematical Concepts

Calculus
Arc Length
Integral Calculus
Graphing

Formulas

Arc Length: L = ∫_a^b sqrt(1 + (dy/dx)^2) dx
Derivative: dy/dx

Theorems

Arc Length Formula

Suitable Grade Level

Grades 11-12