Why is z = rcos(θ) and not z = rsin(θ) in surface integrals?

In summary, when looking at the paint doc, the question was raised about why z is equal to rcos(θ) and not rsin(θ) when x is also equal to rcos(θ). However, it was pointed out that the set-up is symmetric between x and z, so it does not matter which variable is equated with the cosine and which with the sine. The individual asking the question then tried using sine and got a different answer, but it was confirmed that the answers are indeed the same.
  • #1
Miike012
1,009
0
Look in the paint doc. I was wondering why they said z = rcos(θ) and not z = rsin(θ) and x = rcos(θ)
 

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  • #2
The set-up is symmetric between x and z, so does it matter which is equated with the cos and which with the sin?
 
  • #3
haruspex said:
The set-up is symmetric between x and z, so does it matter which is equated with the cos and which with the sin?

Well when i used sine I came out with a different answer but ill try again.
 
  • #4
haruspex said:
The set-up is symmetric between x and z, so does it matter which is equated with the cos and which with the sin?

You are right the answers are the same. thanks.
 

FAQ: Why is z = rcos(θ) and not z = rsin(θ) in surface integrals?

What is a surface integral?

A surface integral is a mathematical concept used in multivariable calculus to calculate the flux or flow of a vector field through a surface. It is a generalization of the concept of a line integral to higher dimensions.

How is a surface integral different from a regular integral?

A surface integral involves integrating over a two-dimensional surface, while a regular integral involves integrating over a one-dimensional curve. Additionally, the integrand of a surface integral is a vector field, while the integrand of a regular integral is a scalar function.

What is the purpose of using a surface integral?

Surface integrals are used in many areas of science and engineering, such as physics, fluid mechanics, and electromagnetism. They allow us to calculate important quantities such as flux, work, and surface area.

How do you set up a surface integral?

To set up a surface integral, you need to define the surface you are integrating over and the vector field that you are integrating. This can be done using parametric equations or by defining the surface as a level surface of a function. The limits of integration are then determined by the boundaries of the surface.

Are there any applications of surface integrals in real life?

Yes, surface integrals have many real-life applications. For example, in fluid mechanics, they are used to calculate the rate of fluid flow through a surface. In electromagnetism, they are used to calculate the electric or magnetic flux through a surface. They are also used in computer graphics to calculate lighting and shading effects on curved surfaces.

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