Grasshopper- normal vector line of sin curve

Hi, everyone.

I want to create this object in grasshopper, but I cannot.

I want to draw a vector-normal of sin curve that maximizes the length in the +Y direction with π I/2 and in the -Y direction with π 3/4.
I want to learn how to draw this vector line.
So I want to ask anyone who can tell me.
I am sorry to trouble you, but I appreciate your cooperation.

Have a look at the attachment. (10.2 KB)


Thank you for your reply.
and your explanation was thorough.
I will try soon!