else if(getValue().equals("sqrt")){
            DifferentialTree left, right;
            left = new DifferentialTree("1 * " + getLeftChild().differentiate().toString());
            if(findOuterOperatr(removeUnnecessaryParenthesis(getLeftChild().toString())) != -1)
                right = new DifferentialTree("2 * sqrt"+getLeftChild().toString());
            else
                right = new DifferentialTree("2 * sqrt("+getLeftChild().toString()+")");
            return new DifferentialTree("/", left, right, getParent());
        }