Hi
Thx for the answer.
> You're converting expression to polar form incorrectly.
Yes but where is my error ?
>
> You should get r=r(theta) from {r=r(t),theta=theta(t)} by excluding parameter
> t (which is not an argument).
I have changed name "t" to "theta" ( I didn't know that it has meaning)
but it gives the same curve.
Anyway, it's better to start from known polar equation of cardioid
>
> r = a (1-cos(theta)).
>
> So, parametric equations are ...
Yes parametric form works well.
Can it be done in polar form ?
(:-))
Adam