# Getting 3D parametric equation to work with x,y values

sal22 shared this question 11 months ago

I have 2 questions.

1) I have a 3D parametric equation below that I would like to animate with geogebra but the Z variable (inputbox) doesn't seem to accept the x and y values. How can I fix this? (I've attached the ggb file also)

The plot is suppose to look something like this.

If you want to see how it was generated the Octave code can be found here

What I'm trying to model:

2) How can I change the equation to have the sides be pushed up more and to the right at a steeper angle like the Lily Impeller image? The Left image is what I get plotting the equation and the right Image is what I'm trying to get to.

me (x^2+y^2=u^2 cos(v)^2 as Chris said)

https://www.geogebra.org/m/twfwsxb9

2

One thing: instead of using x and y for z, I gues you have to repeat the expressions for x and y. So I guess you're getting something as Surface(u*sin(u)cos(u), u*cos(u)cos(v), -u*sin(v)-sin(pi/3)*sqrt((u*sin(u)cos(u))²+(u*cos(u)cos(v))²), u, 0°, 360°, v, 0°, 360°)Probably I missed something because the result is quite different.

2

me (x^2+y^2=u^2 cos(v)^2 as Chris said)

https://www.geogebra.org/m/twfwsxb9

1

Thanks!!

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