如果x接近某个值时为Statement [英] If Statement when x is near a value

问题描述

我正在尝试解决数值方程式：

I am trying to solve the numerical equation:

sin ^ 2（x）tan（x）= 0.499999

sin^2(x)tan(x) = 0.499999

在C.
中使用while循环但是如果我舍入到0.5，我只能得到打印答案的程序。这让我想到，有没有一种写作方式：

Using a while loop in C. However I was only able to get program to print an answer if I rounded to 0.5. This led me to thinking, is there a way of writing:

For(x=0;x<=360;x=x+0.001)
{ y=f(x)
If(y **is near x**(e.g. Within 1 percent) )
Do something etc.
}

如果值足够接近，有没有办法告诉计算机执行任务。比如在这个if语句中？
谢谢。

Is there a way of telling the computer to execute a task if the value is sufficiently near. Such as in this if statement? Thank you.

推荐答案

使用相对差异，例如：

#include <math.h>

static inline double reldiff(double x, double y)
{
    return fabs(x - y) / fmax(fabs(x), fabs(y));
}

现在您的测试成为：

if (reldiff(x, y) < 0.01)   // 1% as requested

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