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常用数学函数

计算反余弦 （arccos(x)）

std::acos, 
std::acosf, 
std::acosl

定义于头文件 <math.h>
float       acosf( float arg );	(1)	(C99 起)
double      acos( double arg );	(2)
long double acosl( long double arg );	(3)	(C99 起)
定义于头文件 <tgmath.h>
#define acos( arg )	(4)	(C99 起)

1-3) 计算 arg 的弧（反）余弦主值。

4) 泛型宏：若参数拥有 long double 类型，则调用 acosl 。否则，若参数拥有整数类型或 double 类型，则调用 acos 。否则调用 acosf 。若参数为复数，则宏调用对应的复数函数（ cacosf 、 cacos 、 cacosl ）。

参数

arg

-

浮点值

返回值

若不出现错误，则返回 arg 于范围 [0 ; π] 中的弧（反）余弦（ arccos(arg) ）。

若出现定义域错误，则返回实现定义值（受支持平台上为 NaN ）。

若出现下溢所致的值域错误，则返回（舍入后的）正确结果。

错误处理

报告 math_errhandling 中指定的错误。

若 arg 在范围 [-1.0; 1.0] 外则出现定义域错误。

若实现支持 IEEE 浮点算术（ IEC 60559 ），则

• 若参数为 +1 ，则返回值 +0 。
• 若 |arg| > 1 ，则返回定义域错误并返回 NaN 。
• 若参数为 NaN ，则返回 NaN 。

调用示例

#include <iostream>
#include <cstdlib>
#include <typeinfo>
#include <cinttypes>
#include <cmath>
#include <math.h>
#include <tgmath.h>int main()
{//1-3) 计算 arg 的弧（反）余弦主值。const float fNumber = std::acos(-1);std::cout << "typeid(float).name():   " << typeid(float).name() << std::endl;for (int i = 1; i <= 10; i += 1){std::cout << "std::acos(" << fNumber / i << "):   "<< std::acos(fNumber / i) << std::endl;}std::cout << std::endl;for (int i = 1; i <= 10; i += 1){std::cout << "std::acos(" << - fNumber / i << "):   "<< std::acos(- fNumber / i) << std::endl;}std::cout << std::endl;const double dNumber = std::acos(-1);for (int i = 1; i <= 10; i += 1){std::cout << "std::acos(" << dNumber / i << "):   "<< std::acos(dNumber / i) << std::endl;}std::cout << std::endl;for (int i = 1; i <= 10; i += 1){std::cout << "std::acos(" << - dNumber / i << "):   "<< std::acos(- dNumber / i) << std::endl;}std::cout << std::endl;const long double ldNumber = std::acos(-1);std::cout << "typeid(long double).name():   " << typeid(long double).name() << std::endl;for (int i = 1; i <= 10; i += 1){std::cout << "std::acos(" << ldNumber / i << "):   "<< std::acos(ldNumber / i) << std::endl;}std::cout << std::endl;for (int i = 1; i <= 10; i += 1){std::cout << "std::acos(" << - ldNumber / i << "):   "<< std::acos(- ldNumber / i) << std::endl;}std::cout << std::endl;return 0;
}

输出

typeid(float).name():   f
std::asin(3.14159):   nan
std::asin(1.5708):   nan
std::asin(1.0472):   nan
std::asin(0.785398):   0.903339
std::asin(0.628319):   0.67939
std::asin(0.523599):   0.55107
std::asin(0.448799):   0.465421
std::asin(0.392699):   0.403565
std::asin(0.349066):   0.356574
std::asin(0.314159):   0.319571std::asin(-3.14159):   nan
std::asin(-1.5708):   nan
std::asin(-1.0472):   nan
std::asin(-0.785398):   -0.903339
std::asin(-0.628319):   -0.67939
std::asin(-0.523599):   -0.55107
std::asin(-0.448799):   -0.465421
std::asin(-0.392699):   -0.403565
std::asin(-0.349066):   -0.356574
std::asin(-0.314159):   -0.319571std::asin(3.14159):   nan
std::asin(1.5708):   nan
std::asin(1.0472):   nan
std::asin(0.785398):   0.903339
std::asin(0.628319):   0.67939
std::asin(0.523599):   0.55107
std::asin(0.448799):   0.465421
std::asin(0.392699):   0.403565
std::asin(0.349066):   0.356574
std::asin(0.314159):   0.319571std::asin(-3.14159):   nan
std::asin(-1.5708):   nan
std::asin(-1.0472):   nan
std::asin(-0.785398):   -0.903339
std::asin(-0.628319):   -0.67939
std::asin(-0.523599):   -0.55107
std::asin(-0.448799):   -0.465421
std::asin(-0.392699):   -0.403565
std::asin(-0.349066):   -0.356574
std::asin(-0.314159):   -0.319571typeid(long double).name():   e
std::asin(3.14159):   nan
std::asin(1.5708):   nan
std::asin(1.0472):   nan
std::asin(0.785398):   0.903339
std::asin(0.628319):   0.67939
std::asin(0.523599):   0.55107
std::asin(0.448799):   0.465421
std::asin(0.392699):   0.403565
std::asin(0.349066):   0.356574
std::asin(0.314159):   0.319571std::asin(-3.14159):   nan
std::asin(-1.5708):   nan
std::asin(-1.0472):   nan
std::asin(-0.785398):   -0.903339
std::asin(-0.628319):   -0.67939
std::asin(-0.523599):   -0.55107
std::asin(-0.448799):   -0.465421
std::asin(-0.392699):   -0.403565
std::asin(-0.349066):   -0.356574
std::asin(-0.314159):   -0.319571