能不能介绍下c语言中math.h中的函数的名称和功能？

Posted 2023-05-16

就是math.h中各个函数的名称，功能~
格式比如：
abs（int x）表示求x的绝对值。
……
谢谢了~

abs() 好像是stdlib.h的函数吧？

math.h
The math header defines several mathematic functions.

Macros:

HUGE_VAL
Functions:

acos();
asin();
atan();
atan2();
ceil();
cos();
cosh();
exp();
fabs();
floor();
fmod();
frexp();
ldexp();
log();
log10();
modf();
pow();
sin();
sinh();
sqrt();
tan();
tanh();

2.7.1 Error Conditions
All math.h functions handle errors similarly.

In the case that the argument passed to the function exceeds the range of that function, then the variable errno is set to EDOM. The value that the function returns is implementation specific.

In the case that the value being returned is too large to be represented in a double, then the function returns the macro HUGE_VAL, and sets the variable errno to ERANGE to represent an overflow. If the value is too small to be represented in a double, then the function returns zero. In this case whether or not errno is set to ERANGE is implementation specific.

errno, EDOM, and ERANGE are defined in the errno.h header.

Note that in all cases when it is stated that there is no range limit, it is implied that the value is limited by the minimum and maximum values of type double.

2.7.2 Trigonometric Functions
2.7.2.1 acos
Declaration:

double acos(double x);
Returns the arc cosine of x in radians.

Range:

The value x must be within the range of -1 to +1 (inclusive). The returned value is in the range of 0 to pi (inclusive).

2.7.2.2 asin
Declaration:

double asin(double x);
Returns the arc sine of x in radians.

Range:
The value of x must be within the range of -1 to +1 (inclusive). The returned value is in the range of -p/2 to +p/2 (inclusive).
2.7.2.3 atan
Declaration:
double atan(double x);
Returns the arc tangent of x in radians.

Range:
The value of x has no range. The returned value is in the range of -p/2 to +p/2 (inclusive).
2.7.2.4 atan2
Declaration:
double atan2(doubly y, double x);
Returns the arc tangent in radians of y/x based on the signs of both values to determine the correct quadrant.

Range:
Both y and x cannot be zero. The returned value is in the range of -p/2 to +p/2 (inclusive).
2.7.2.5 cos
Declaration:
double cos(double x);
Returns the cosine of a radian angle x.

Range:
The value of x has no range. The returned value is in the range of -1 to +1 (inclusive).
2.7.2.6 cosh
Declaration:
double cosh(double x);
Returns the hyperbolic cosine of x.

Range:
There is no range limit on the argument or return value.
2.7.2.7 sin
Declaration:
double sin(double x);
Returns the sine of a radian angle x.

Range:
The value of x has no range. The returned value is in the range of -1 to +1 (inclusive).
2.7.2.8 sinh
Declaration:
double sinh(double x);
Returns the hyperbolic sine of x.

Range:
There is no range limit on the argument or return value.
2.7.2.9 tan
Declaration:
double tan(double x);
Returns the tangent of a radian angle x.

Range:
There is no range limit on the argument or return value.
2.7.2.10 tanh
Declaration:
double tanh(double x);
Returns the hyperbolic tangent of x.

Range:
The value of x has no range. The returned value is in the range of -1 to +1 (inclusive).
2.7.3 Exponential, Logarithmic, and Power Functions
2.7.3.1 exp
Declaration:
double exp(double x);
Returns the value of e raised to the xth power.

Range:
There is no range limit on the argument or return value.
2.7.3.2 frexp
Declaration:
double frexp(double x, int *exponent);
The floating-point number x is broken up into a mantissa and exponent.
The returned value is the mantissa and the integer pointed to by exponent is the exponent. The resultant value is x=mantissa * 2^exponent.

Range:
The mantissa is in the range of .5 (inclusive) to 1 (exclusive).
2.7.3.3 ldexp
Declaration:
double ldexp(double x, int exponent);
Returns x multiplied by 2 raised to the power of exponent.
x*2^exponent

Range:
There is no range limit on the argument or return value.
2.7.3.4 log
Declaration:
double log(double x);
Returns the natural logarithm (base-e logarithm) of x.

Range:
There is no range limit on the argument or return value.
2.7.3.5 log10
Declaration:
double log10(double x);
Returns the common logarithm (base-10 logarithm) of x.

Range:
There is no range limit on the argument or return value.
2.7.3.6 modf
Declaration:
double modf(double x, double *integer);
Breaks the floating-point number x into integer and fraction components.
The returned value is the fraction component (part after the decimal), and sets integer to the integer component.

Range:
There is no range limit on the argument or return value.
2.7.3.7 pow
Declaration:
double pow(double x, double y);
Returns x raised to the power of y.

Range:
x cannot be negative if y is a fractional value. x cannot be zero if y is less than or equal to zero.
2.7.3.8 sqrt
Declaration:
double sqrt(double x);
Returns the square root of x.

Range:
The argument cannot be negative. The returned value is always positive.
2.7.4 Other Math Functions
2.7.4.1 ceil
Declaration:
double ceil(double x);
Returns the smallest integer value greater than or equal to x.

Range:
There is no range limit on the argument or return value.
2.7.4.2 fabs
Declaration:
double fabs(double x);
Returns the absolute value of x (a negative value becomes positive, positive value is unchanged).

Range:
There is no range limit on the argument. The return value is always positive.
2.7.4.3 floor
Declaration:
double floor(double x);
Returns the largest integer value less than or equal to x.

Range:
There is no range limit on the argument or return value.
2.7.4.4 fmod
Declaration:
double fmod(double x, double y);
Returns the remainder of x divided by y.

Range:
There is no range limit on the return value. If y is zero, then either a range error will occur or the function will return zero (implementation-defined).

参考资料：http://www.acm.uiuc.edu/webmonkeys/book/c_guide/2.7.html

参考技术A 在每本教科书的最后几页都有啊！～

C语言编译包含math库加参数-lm

在 Linux 系统下，C 源文件若调用了 math 库里的函数，则编译时要加上 -lm （是字母 l ，不是数字 1），表示链接到 math 库。

文件名称：1.c
#include<stdio.h>
#include<math.h>               //程序中要调用求平方根函数 sqrt

int main(){
    double a,b,c,disc,x1,x2,p,q;
    scanf("%lf%lf%lf",&a,&b,&c);
    disc = b * b - 4 * a * c;
    p = -b / (2.0 * a);
    q = sqrt(disc) / (2.0 * a);
    x1 = p + q,x2 = p - q;
    printf("x1=%7.2f\\nx2=%7.2f\\n",x1,x2);
    return 0;
}

那么：

gcc 1.c -lm

原因

因为数学函数位于 libm.so 库文件中（这些库文件通常位于 /lib 目录下），
-lm 选项告诉编译器，我们程序中用到的数学函数要到这个库文件里找。

而 printf 为什么不需要呢？
这是因为它位于 libc.so 库文件中，
使用 libc.so 中的库函数在编译时不需要加 -lc 选项，
当然加了也不会错，因为这个选项是 gcc 的默认选项。