String sqrt() {
	    cleanX = true;
	    cleanY = true;
	    endZero = "";
	    if (enterX) {
	        x = Math.sqrt(x);
	        return format(x);
	    } else if (! canCalculate) {
	        x = Math.sqrt(x);
	        return format(x);
	    } else {
	        y = Math.sqrt(y);
	        return format(y);
	    }
	}