Question

我被要求按照这个等式找到cos：

我能够找到角度的罪，但是当找到cos时，我得到的数字与正确的值完全不同：

我使用以下代码来查找cos。 ps：我不能使用math.cos

public static double cos(double x, int n){

    // declaring cos and factorial

    double cos = 0.0;


    // this loop determines how long does the loop go so the answer is more accurate
    for (long howlong = 1 ; howlong <=n; howlong++){
        double factorial =1;

    // this will calculate the factorial for even numbers ex/ 2*2 = 4 , 4-2 = 2
    // for the denominator 

    for (int factorialnumber=1; factorialnumber<=2*howlong-2; factorialnumber++){
        factorial = factorial * howlong;    

    }

    // now we need to create the pattern for the + and -
    // so we use % that switches the sign everytime i increments by 1

    if (howlong%2==1){
        cos = cos + (double) (Math.pow(x, 2*howlong-2)/factorial);
    }

    else{
        cos = cos - (double) (Math.pow(x, 2*howlong-2)/factorial);
    }
    }
    return cos;
}

编辑：我弄清楚了我的错误，因为它将阶乘乘以多长而不是阶乘数。

Answer 1

你有两个错误。

（错误1）你写的地方

factorial = factorial * howlong;

应该是

factorial = factorial * factorialnumber;

（错误2）您未通过外部循环重置每次迭代的因子。所以你需要移动线

double factorial =1;

向下几行，以便它在外环内。

如果您进行了这两项更改，那么cos(Math.PI / 6, 10)的结果为0.8660254037844386，这对我来说是正确的。

Answer 2

你的阶乘的计算是错误的。尝试使用此代码：

@IBDesignable class AttributedTextView: UITextView {

    private let placeholderLabel = UILabel()

    @IBInspectable var placeholder: String = "" {

        didSet {

            setupPlaceholderLabelIfNeeded()
            textViewDidChange()
        }
    }

    override var text: String! {

        didSet {
            textViewDidChange()
        }
    }

    //MARK: - Initialization

    override func awakeFromNib() {
        super.awakeFromNib()

        setupPlaceholderLabelIfNeeded()
        NotificationCenter.default.addObserver(self, selector: #selector(textViewDidChange), name: .UITextViewTextDidChange, object: nil)
    }

    //MARK: - Deinitialization

    deinit {
        NotificationCenter.default.removeObserver(self)
    }

    //MARK: - Internal

    func textViewDidChange() {

        placeholderLabel.isHidden = !text.isEmpty
        layoutIfNeeded()
    }

    //MARK: - Private

    private func setupPlaceholderLabelIfNeeded() {

        placeholderLabel.removeFromSuperview()
        placeholderLabel.frame = CGRect(x: 0, y: 8, width: frame.size.width, height: 0)
        placeholderLabel.textColor = UIColor.lightGray
        placeholderLabel.text = placeholder

        placeholderLabel.sizeToFit()

        insertSubview(placeholderLabel, at: 0)
    }
}

Answer 3

您的计算不正确，请转到

 double value = 1;
            for (int factorialnumber = 1; factorialnumber <= 2 * howlong - 2; factorialnumber++) {
                value = factorialnumber * value;
            }

            factorial = value;
            System.out.println(value + " " + (2 * howlong - 2));

在java中查找角度的cos

3 个答案: