How can I draw this graph ( equiangular spiral antenna) using following functions and plot?

r1= r0.exp(a*phi);
r2= r0.exp(a*(phi-delta));
r3= r0.exp(a*(phi+pi));
r4 = r0.exp(a*(phi-delta+pi));
Delta = pi/2
r0 = 0.5
a = 0.5 rad
phi = 0:pi/36:2*pi

[darova]

It doesn't work

How to make it work?

[Anh Phan Viet]

Sorry, it is : r1 = r0*exp(a*phi), also similarly: r2, r3, r4

[darova]

Here is what i got when run your script

What do you want to do with it?

[Anh Phan Viet]

That's also what I've had when I run, but it should ideally look like the image I 've posted: Two - arm equiangular spiral antenna.

[darova]

I found these formulas on Wiki

[Anh Phan Viet]

Thanks a lot. I 've now managed to create this

[darova]

0_0

congratulations!