Method graph

__test__/theorem.js:724–730

(f, from=-100, to=100, step=0.1)

  	return slope
  }
  graph(f, from=-100, to=100, step=0.1) {
  	let array = {}
  	for (var i = new BigNumber(from); i.lessThanOrEqualTo(new BigNumber(to)); i = i.plus(new BigNumber(step))) {
  		array[i.toString()] = f.core(i).toFixed(15)
  	}
  	return array
  }
  integrate(poly) {
  	if (poly.type != 'polynomial') {
  		throw "TheoremJS: Integrate: Not a polynomial"