[Switch] common mathematical functions and constants iOS development of

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Objective-c introduce common functions, constants, variables

Arithmetic Functions

Function name	Explanation
int rand()	Random number generator. (Example) srand (time (nil)); // random number initialization int val = rand () P; // a random number between 0 to 49
int abs(int a)	The absolute value of the integer (e) int val = abs (-8); → 8 ※ float when used fabs.
double fabs(double a)	Floating-point absolute value (for example) double val = fabs (-12.345); → 12.345 ※ integer time with abs.
double floor(double a)	And the floating point integer part (decimal discarded) (Example) double val = floor (12.345); → 12.000
double ceil(double a);	And the floating point integer part (decimal part discarded, to enter digit 1) (Example) double val = ceil (12.345); → 13.000
double pow(double a, double b)	a power of b (Example) double val = pow (2, 3); → 8
double sqrt(double a)	a square root of (e) double val = sqrt (2); → 1.41421356

Trigonometric functions

Function name	Explanation
double cos(double a)	Cosine function (a: radian)
double sin(double a)	Sine function (a: radian)
double tan(double a)	Tangent function (a: radian)
double asin(double a)	Arcsine (a: radian)
double acos(double a)	Inverse cosine function (a: radian)
double atan(double a)	Arc tangent function
double atan2(double a, double b)	Returns the given coordinate values ​​of a and b arctangent

Exponential function

Function name	Explanation
double log(double a)	Logarithm to the base e
double log10(double a)	Logarithmic function log

constant

Constant name	Explanation
M_PI	Pi (= π)
M_PI_2	Pi 1/2 (= π / 2)
M_PI_4	Pi 1/4 (= π / 4)
M_1_PI	= 1 / p
M_2_PI	= 2 / n
M_E	=e
M_LOG2E	log_2(e)
M_LOG10E	log_10(e)