Finding integral of a helicoid

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SUMMARY

The discussion centers on evaluating the integral \(\int\int \sqrt{1+x^2+y^2}\) over the helicoid defined by the parametric equation \(r(u,v) = u \cos(v)i + u \sin(v)j + vk\) for \(0 \leq u \leq 1\) and \(0 \leq v \leq \theta\). Participants emphasize the necessity of transforming the integral into an appropriate coordinate system, suggesting the use of spherical coordinates for simplification. It is crucial to apply the Jacobian when changing coordinate systems, as this affects the integral's evaluation. The discussion highlights the importance of understanding the relationships between Cartesian, polar, cylindrical, and spherical coordinates.

PREREQUISITES
  • Understanding of parametric equations, specifically helicoids.
  • Knowledge of coordinate transformations, including Cartesian, polar, cylindrical, and spherical coordinates.
  • Familiarity with the concept of the Jacobian in multivariable calculus.
  • Basic proficiency in evaluating double integrals.
NEXT STEPS
  • Learn how to apply the Jacobian for coordinate transformations in integrals.
  • Study the evaluation of double integrals in spherical coordinates.
  • Explore examples of integrals over helicoids and similar surfaces.
  • Review the relationships between different coordinate systems in multivariable calculus.
USEFUL FOR

Students and educators in calculus, particularly those focusing on multivariable calculus and integral evaluation techniques, will benefit from this discussion.

MasterWu77
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Homework Statement


Evaluate \int\int \sqrt{1+x^2+y^2} where S is the helicoid: r(u,v) = u cos(v)i + u sin(v)j+vk , with 0\lequ\leq1, 0\leqv\leq\theta.

The S is the area that we are trying to find. the area of the integral i guess.

Homework Equations



I know i have to use the \varphi (\theta,\phi) = (acos\theta sin \phi, asin\theta sin \phi, acos\phi)



The Attempt at a Solution


we did examples like this in class but I'm not sure where to start off. do i need to change the equation of the integral into sin and cos?
 
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you don't HAVE to use phi(theta,phi), you can do this in cartesian coordinates... but i think it would be easier to use a different coordinate system. ( i would suggest trying spherical?)

Yes, I you have to change the object of the integral if you want to use a different coordinate system because "x" and "y" are normally used for cartesian coordinates. theta and r are used for polar coordinates, theta, r and z are used for cylindrial coordinates, phi, rho, and theta are typically used for spherical coordinates.

All of these are just variables tho and can really be anything. They stand for angles and radii of the problem.

Remeber tho, when you change the coordinate system of your integral you have to apply the jacobian. ie, for cylindrical coordinates, the r dr dtheta is appended to the integral, or sphereical is some other trig with phi and theta.

Hope this helps somewhat...
 

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