Определение знака функции

(function() {
	'use strict';
	NAinfo.requireApiVersion(0, 0);

	function CanUseFunc(func, gr) {
		switch (func) {
		case 0:
			if (!gr || gr == 1)
				return false;
			return true;
		case 1:
				if (Math.abs(gr)>=0.5 || gr==1.5)
				return false;
			return true;
		}
	};

	function WhatIsSignOfFunction(func, gr, shag) {//определяет знак

		if (gr >= 0)
			while (gr > 1.5)
				gr -= 2;
		else
			while (gr < 1.5)
				gr += 2;

		if (shag>= 1) {
			if (func > 2||shag>1)
				return undefined;
			if (!CanUseFunc(func, gr))
				return undefined;
		}
		switch (func) {
		case 0:
			if (gr >= 0.5 && (gr + 0.5) <= 1.5)
				return -1;
			else
				return 1;
		case 1:
			if (gr >= 1 && (gr + 0.5) <= 2)
				return -1;
			else
				return 1;
		case 2:
			if ((gr >= 0.5 && (gr + 0.5) <= 1) || (gr >= 1.5 && (gr + 0.5) <= 2))
				return -1;
			else
				return 1;
		}
	};
	let k = sluchch(-2, 2, 0.5);
	let shag=sluchch(0.5,1,0.5);
	let h = WhatIsSignOfFunction(0, k, shag);
	let ugol;
	if (k >= -0.5)
		ugol = `(${k.texfracpi(1)};${(k+shag).texfracpi(1)})`;
	else
		ugol = `(${(k+shag).texfracpi(1)};${k.texfracpi(1)})`;
	NAtask.setTask({
		text: `$\\cos\\in ${ugol}$ ${h}`,
		answers: 0,
	});
})();