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Homework Help Overview

The problem involves finding the length of the curve defined by the equation y = x^3, starting from the point P(1,1). The context is calculus, specifically focusing on arc length calculation using integral calculus.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the initial steps taken to find the derivative and set up the integral for arc length. There is uncertainty regarding the appropriate technique for evaluating the integral, with suggestions of using trigonometric substitution and references to elliptic integrals. Questions are raised about the endpoint of the integral and whether the task is to find a general expression for the length or a specific numerical value.

Discussion Status

The discussion is ongoing, with participants exploring different mathematical techniques and questioning the assumptions regarding the endpoints of the integral. Some guidance has been offered regarding the complexity of the integral and potential numerical methods for approximation.

Contextual Notes

There is a noted ambiguity about whether an endpoint is provided for the integral, which affects the approach to finding the length of the curve. Participants are also considering the implications of the problem's constraints on the methods used.

MillerGenuine
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Homework Statement



Find the length of the curve y=x^3 using P(1,1) as the starting point

Homework Equations




<br /> f(x) = \int_{a}^{x} {\sqrt 1 + {f&#039;(t)}^2}<br />



The Attempt at a Solution



So far all I've done is found my y' and plugged it in, giving me 1+9t^4 inside the square root...now from here I am not sure whate technique to use to do the integral.
 
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looks like a classic trig sub integral
 
lanedance said:
looks like a classic trig sub integral

If only. Checking Wolfram-Alpha, you'll require the Elliptic Integral of the First kind to solve this. A simple trig sub works with functions of the form sqrt(a^2 + (bx)^2), but not sqrt(a^4 + (bx)^4).
 
fair bump, play on
 
MillerGenuine said:

Homework Statement



Find the length of the curve y=x^3 using P(1,1) as the starting point

Homework Equations




<br /> f(x) = \int_{a}^{x} {\sqrt 1 + {f&#039;(t)}^2}<br />



The Attempt at a Solution



So far all I've done is found my y' and plugged it in, giving me 1+9t^4 inside the square root...now from here I am not sure whate technique to use to do the integral.
Is there an end point given? If so, you run into the problem pointed out by Char Limit. If not, are you just supposed to find an expression that represents the length from (1, 1) to an arbitrary point (x, x3)?

If it's the latter, here's a function that gives the length along the curve. Although difficult to integrate analytically, it can be approximated by a number of numerical integration techniques.
L(x) = \int_1^x \sqrt{1 + 9t^4}dt
 

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