@Kitonum 

I wasn't expressing my variables correctly I think. Thanks so much!

@Kitonum

Awesome! That worked really well - thanks very much!

Can I plot this cone on the same grid as a proc (it's the curve you helped me with before)? 

I've tried this:

display({Cone, Curve}, axes = boxed, scaling = constrained)

but I get an error.

Thanks!

@Kitonum 

Hi, I have done a lot of fiddling and have now managed to get it to work! Thanks so much for the help!

@Kitonum 

I have attached my maple worksheet:

Plots.mw

I am now having to use maple 2015.

Sorry and thanks so much!

@Kitonum 

Sorry for the late reply - I've been away.

Thanks so much for all your help!

I've been through it again and realised my formula for phi was wrong. I have now adjusted it but get the follwing error:

Error, in phi, too many levels of recursion

Is there anything I can do about this?

@acer

Sorry I meant I couldn't get it it to work using my formulae:

(theta is just a constant)

thanks!

@Kitonum 

Thanks for your response! I have tried this but get the following error:

Warning, unable to evaluate the function to numeric values in the region; see the plotting command's help page to ensure the calling sequence is correct

What does this mean?