How to fix chart with fixed start and end to user input?

Question

JavaScript

I made a graph of sin (x) on the interval (0; 2P) using canvas.
How to remake it so that the interval is entered by the user? Variables storing values ​​that the user enters:

start = document.all.start.value;
finish = document.all.finish.value;

Answer 1

https://jsfiddle.net/twobomb/v2dsyfz0/