CODEWITHSUNDEEP
cmatlabmath.h
Matthew The Terrible
Matthew The Terrible

Reputation: 1643

c equavilent to matlab's sind and cosd function

So I am working with some matlab code converting to c code by hand. I am just wondering if there is a c equivalent to the sind and cosd functions I'm seeing in the matlab code. I guess this returns the answer in degrees rather than the c sin and cos function that gives the result in radians. I guess I could just multiply the result by 180/pi but was just wondering if there was a library function in math.h I'm not seeing. Or even if there is something in the gsl library that does that.

Upvotes: 5

Views: 8031

Answers (5)

Stuart
Stuart

Reputation: 885

Also, note that sind and cosd etc do not return a result in degrees, they take their arguments in degrees. It is asind and acosd that return their results in degrees.

Upvotes: 1

R.. GitHub STOP HELPING ICE
R.. GitHub STOP HELPING ICE

Reputation: 215507

H2CO3's solution will have catastrophic loss of precision for large arguments due to the imprecision of M_PI. The general, safe version for any argument is:

#define sind(x) (sin(fmod((x),360) * M_PI / 180))

Upvotes: 10

meyumer
meyumer

Reputation: 5064

No, they are not available in C library. You will only find radian value arguments or return values in C library.

Upvotes: 1

user529758
user529758

Reputation:

No, the trigonometric functions in the C standard library all work in radians. But you can easily get away with a macro or an inline function:

#define sind(x) (sin((x) * M_PI / 180))

or

inline double sind(double x)
{
    return sin(x * M_PI / 180);
}

Note that the opposite of the conversion is needed when you want to alter the return value of the function (the so-called inverse or "arcus" functions):

inline double asind(double x)
{
    return asin(x) / M_PI * 180;
}

Upvotes: 3

ouah
ouah

Reputation: 145899

Not in the C library. All trigonometric C library functions take arguments as radian values not degree. As you said you need to perform the conversion yourself or use a dedicated library.

Upvotes: 0

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