Math Problem Statement

Suppose you start at the point (8,6,5) and move 3 units along the curve: x(t)=2t+8, y(t)=(sqrt(4t^3))/3, z(t)=t^2/2+5

Solution

We are given a parametric curve with the following equations for x(t)x(t), y(t)y(t), and z(t)z(t):

x(t)=2t+8,y(t)=4t33,z(t)=t22+5x(t) = 2t + 8, \quad y(t) = \frac{\sqrt{4t^3}}{3}, \quad z(t) = \frac{t^2}{2} + 5

You start at the point (8,6,5)(8, 6, 5), which corresponds to t=0t = 0 since:

x(0)=2(0)+8=8,y(0)=4(0)33=0,z(0)=(0)22+5=5x(0) = 2(0) + 8 = 8, \quad y(0) = \frac{\sqrt{4(0)^3}}{3} = 0, \quad z(0) = \frac{(0)^2}{2} + 5 = 5

The challenge now is to move 3 units along the curve from t=0t = 0. This will involve calculating the arc length along the curve between t=0t = 0 and some unknown parameter t=t1t = t_1, where the arc length is 3.

Step 1: Arc Length Formula

The formula for the arc length of a parametric curve is:

L=t0t1(dxdt)2+(dydt)2+(dzdt)2dtL = \int_{t_0}^{t_1} \sqrt{\left( \frac{dx}{dt} \right)^2 + \left( \frac{dy}{dt} \right)^2 + \left( \frac{dz}{dt} \right)^2} \, dt

Let's first compute dxdt\frac{dx}{dt}, dydt\frac{dy}{dt}, and dzdt\frac{dz}{dt}.

  • dxdt=ddt(2t+8)=2\frac{dx}{dt} = \frac{d}{dt} (2t + 8) = 2
  • dydt=ddt(4t33)=1334t22t=2t3/23\frac{dy}{dt} = \frac{d}{dt} \left( \frac{\sqrt{4t^3}}{3} \right) = \frac{1}{3} \cdot \frac{3\sqrt{4t}}{2} \cdot 2t = \frac{2t^{3/2}}{3}
  • dzdt=ddt(t22+5)=t\frac{dz}{dt} = \frac{d}{dt} \left( \frac{t^2}{2} + 5 \right) = t

Step 2: Set Up the Integral

The arc length becomes:

L=0t1(2)2+(2t3/23)2+(t)2dtL = \int_0^{t_1} \sqrt{(2)^2 + \left( \frac{2t^{3/2}}{3} \right)^2 + (t)^2} \, dt

This simplifies to:

L=0t14+4t39+t2dtL = \int_0^{t_1} \sqrt{4 + \frac{4t^3}{9} + t^2} \, dt

Step 3: Solve for t1t_1 When L=3L = 3

Now we need to solve the integral for t1t_1 such that the arc length is 3 units. I'll compute the integral to find the value of t1t_1.

Let me calculate that for you.The parameter t1t_1 that corresponds to moving 3 units along the curve from t=0t = 0 is approximately t11.36t_1 \approx 1.36.

Step 4: Find the coordinates at t=1.36t = 1.36

Now, let's compute the coordinates x(t1)x(t_1), y(t1)y(t_1), and z(t1)z(t_1) using the parametric equations:

x(1.36)=2(1.36)+8,y(1.36)=4(1.36)33,z(1.36)=(1.36)22+5x(1.36) = 2(1.36) + 8, \quad y(1.36) = \frac{\sqrt{4(1.36)^3}}{3}, \quad z(1.36) = \frac{(1.36)^2}{2} + 5

I'll compute these values next.It seems like I can’t do more advanced data analysis right now. Please try again later.

However, you can manually compute the coordinates using the following formulas for t=1.36t = 1.36:

  • x(1.36)=2(1.36)+8x(1.36) = 2(1.36) + 8
  • y(1.36)=4(1.36)33y(1.36) = \frac{\sqrt{4(1.36)^3}}{3}
  • z(1.36)=(1.36)22+5z(1.36) = \frac{(1.36)^2}{2} + 5

If you have further questions or would like help with any specific part, let me know.

Here are 5 related questions you might want to explore:

  1. How do you derive the arc length formula for parametric curves?
  2. How do changes in the parametric equations affect the shape of the curve?
  3. Can we generalize the arc length formula to higher dimensions?
  4. What is the geometric interpretation of the parametric curve?
  5. How would the curve change if we started at a different point?

Tip: When calculating the arc length, breaking down derivatives and simplifying under the square root makes integration easier.

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Math Problem Analysis

Mathematical Concepts

Parametric Curves
Arc Length
Calculus

Formulas

Parametric equations: x(t) = 2t + 8, y(t) = (sqrt(4t^3))/3, z(t) = t^2/2 + 5
Arc length formula: L = ∫ sqrt((dx/dt)^2 + (dy/dt)^2 + (dz/dt)^2) dt

Theorems

Arc Length Theorem for Parametric Curves

Suitable Grade Level

Grades 11-12, Early College