开发用于查找根的Secant方法程序(Developing a Secant Method Program for root finding)

开发用于查找根的Secant方法程序(Developing a Secant Method Program for root finding)

所以我一直在试图开发一个割线方法程序，可以用来找到它的根

f（x）= tanh（x） - （x / 3）

然而答案的输出并不完全。 我找到的每个解决方案似乎都是解决它的更复杂的方法。

x = 2; prevx = x; for i = 1:20 x = x - (tanh(x)-(x/3))*((x-(prevx))/((tanh(x)-(x/3))-(tanh(prevx))-((prevx/3)))); prevx = prevx + x; x end

答案应该是2.987。 尽管出于某种原因我得到了一个负数。

So I have been trying to develop a secant method program that can be used for finding the root of

f(x) = tanh(x) - (x / 3)

However the answer output is nowhere close. Every solution I have found seems a more complex way to solve it.

x = 2; prevx = x; for i = 1:20 x = x - (tanh(x)-(x/3))*((x-(prevx))/((tanh(x)-(x/3))-(tanh(prevx))-((prevx/3)))); prevx = prevx + x; x end

The answer should be 2.987. I am getting a negative number though for some reason.

最满意答案

你应该在这一行中加上术语来代替minus：

x = x - (tanh(x)-(x/3))*((x-(prevx))/((tanh(x)-(x/3))-(tanh(prevx))-((prevx/3))));

加上：

x = x + (tanh(x)-(x/3))*((x-(prevx))/((tanh(x)-(x/3))-(tanh(prevx))-((prevx/3))));

为了得到x的理想结果2.987 。 在循环结束之前还要删除x。

You suppose to add up terms so replace minus in this line:

x = x - (tanh(x)-(x/3))*((x-(prevx))/((tanh(x)-(x/3))-(tanh(prevx))-((prevx/3))));

To a plus:

x = x + (tanh(x)-(x/3))*((x-(prevx))/((tanh(x)-(x/3))-(tanh(prevx))-((prevx/3))));

To get a desired result of 2.987 for x. Also remove x before the end of the loop.