I need some help with math

I know you folks here are much better at math then I am, so maybe you can tell me how to make sure the sine function (drawn along the circle) ends with the same value as it begins with?

EDIT:
Inside this project.

P.S.
The project is now updated, based on the help with math by ttocs2112 below.
It now enables a user to make art like this:

Try this. Basically, you need to get the circumference of the circle and divide it by the number of sine waves.

Looking forward to seeing the cool stuff you'll create with this!

Enjoy!

Wow, that's exactly what I've been hoping for. Thank you very much!

And welcome to the forum!

P.S.
It was not hard to transform your ideas into the turtle geometry and I'd like to make the code even more 'turtle'y.
I guess, the set_angle & point_in_direction_angle blocks is the first thing that could be made more 'turtle'y by replacing them with a single turn_(360/n) block.

My pleasure! And thanks for the welcome!

Cheers