Finding volume using quad function

This is the problem I have to solve. I keep getting an error message though and can't figure out what's wrong with it.

Find the volume of revolving the area of the circle(x-6)^2 +(y-7)^2 =5 about the x-axis.

R= 7+sqrt(5-(x-6)^2)

r= 7-sqrt(5-(x-6)^2)

Volume= quad('circle',(6-sqrt(5)),(6+sqrt(5)))

function [ z ] = circle( R, r )

z= pi(R.)^2 -pi(r.)^2

end

Any help would be great! Thanks

[Andrew Newell]

There are lots of errors. Are you using the MATLAB editor? Put your mouse over any red line and you'll see some specific problems.

[Amanda]

Yes, I am. It doesn't say that there are errors until I run it.

Answer 1

[John D'Errico]

You define a function called circle.

function [ z ] = circle( R, r )
R= 7+sqrt(5-(x-6)2)
r= 7-sqrt(5-(x-6)2)
z= pi(R.)2 -pi(r.)2

It has input arguments R and r. Then you try to define the variables R, r, both of which are functions of something called x. Where did x come from? Did you provide it as an input to circle? (No.) In fact, there is no need to pass in R and r into the function circle if you compute them inside the function!

Next, you don't seem to know matlab syntax. What does this mean:

(x-6)2

????? I think you wanted to square (x-6) ? If so, there IS an operator to raise a number to a power. Learn it. Use it.

At the end of circle, you try to define the output z.

z= pi(R.)2 -pi(r.)2

Again, I think you need to read the beginning matlab tutorials about basic syntax. This line has too many syntax errors in it to list.

[Amanda]

Ahh crap. Sorry I copy and pasted this right over from the files. I'm not an idiot. I know how to use the power operator.

I had both R and r on the outside of the function before. x is from the equation of a circle. I'm not sure what to replace it with in the problem. R and r are what I solved y for in the equation of a circle.

function [ z ] = circle( R, r )

R= 7+sqrt(5-(x-6)^2)

r= 7-sqrt(5-(x-6)^2)

z= pi(R.)^2 -pi(r.)^2

[Amanda]

What value would I make x based off of how I'm revolving the equation of a circle around the x axis which makes a doughnut like shape?

[Amanda]

What value would I make x based off of how I'm revolving the equation of a circle around the x axis which makes a doughnut like shape?

Answer 2

[Andrew Newell]

To follow up on a comment - if you are using a MATLAB editor, you should see something like this:

You will certainly have a red button on the right margin indicating errors. Mouse over the red lines and you will see details.

Also, most of John's comments still apply even after your changes - especially the one about reading some MATLAB tutorials.

[Amanda]

I know what the lines mean. The only thing it says is.. Terminate statement with semicolon to suppress output.

[Amanda]

What value would I make x based off of how I'm revolving the equation of a circle around the x axis which makes a doughnut like shape?