graph1 = function(xp1){
const xp=xp1
const p = plotter();
const f = x => (x ** 2);
const fp = x => (2*x);
const tp= (p,x) => fp(p)*(x-p)+f(p)
const txp= x => tp(xp,x)
p.func( f, { stroke: 'green', width: 3 });
p.func( txp, { stroke: 'red', width: 2 });
p.point(xp,f(xp));
p.tex(String.raw`x=${xp}`, 5, 6, { size: 16, stroke: 'blue', baseline: 'middle' })
return p.node;
}