Creating Sine Waves/curves in function object

Hey guys

currently building a basic FM synth and I'm using a function and line~ object to control the modulation index envelope. I plan on having the envelope loop so I'm using metro to trigger the bang going into the function.

I'm hoping to create a bunch of different shapes for the envelope; saw, square, triangle etc. these are all easy to achieve but i don't know how to draw curves in order to implement a sine wave.

if this isn't really a thing you can do with function, is there any other equivalent method that I could do to achieve the same effect?

Thanks

-L

EDIT: another query, is there any way to change the setdomain value of the function object with the number value of the metro? when i put the output of the number into the right input of the setdomain message and try to change the value, the message loses the setdomain and becomes just the number value.