Tim Bunce >
perl5.004_04 >
Math::Trig

Module Version: 1
Math::Trig - trigonometric functions

use Math::Trig; $x = tan(0.9); $y = acos(3.7); $z = asin(2.4); $halfpi = pi/2; $rad = deg2rad(120);

`Math::Trig`

defines many trigonometric functions not defined by the core Perl which defines only the `sin()`

and `cos()`

. The constant **pi** is also defined as are a few convenience functions for angle conversions.

The tangent

tan

The cofunctions of the sine, cosine, and tangent (cosec/csc and cotan/cot are aliases)

csc cosec sec cot cotan

The arcus (also known as the inverse) functions of the sine, cosine, and tangent

asin acos atan

The principal value of the arc tangent of y/x

atan2(y, x)

The arcus cofunctions of the sine, cosine, and tangent (acosec/acsc and acotan/acot are aliases)

acsc acosec asec acot acotan

The hyperbolic sine, cosine, and tangent

sinh cosh tanh

The cofunctions of the hyperbolic sine, cosine, and tangent (cosech/csch and cotanh/coth are aliases)

csch cosech sech coth cotanh

The arcus (also known as the inverse) functions of the hyperbolic sine, cosine, and tangent

asinh acosh atanh

The arcus cofunctions of the hyperbolic sine, cosine, and tangent (acsch/acosech and acoth/acotanh are aliases)

acsch acosech asech acoth acotanh

The trigonometric constant **pi** is also defined.

$pi2 = 2 * pi;

The following functions

tan sec csc cot asec acsc tanh sech csch coth atanh asech acsch acoth

cannot be computed for all arguments because that would mean dividing by zero or taking logarithm of zero. These situations cause fatal runtime errors looking like this

cot(0): Division by zero. (Because in the definition of cot(0), the divisor sin(0) is 0) Died at ...

or

atanh(-1): Logarithm of zero. Died at...

For the `csc`

, `cot`

, `asec`

, `acsc`

, `acot`

, `csch`

, `coth`

, `asech`

, `acsch`

, the argument cannot be `0`

(zero). For the `atanh`

, `acoth`

, the argument cannot be `1`

(one). For the `atanh`

, `acoth`

, the argument cannot be `-1`

(minus one). For the `tan`

, `sec`

, `tanh`

, `sech`

, the argument cannot be *pi/2 + k * pi*, where *k* is any integer.

Please note that some of the trigonometric functions can break out from the **real axis** into the **complex plane**. For example `asin(2)`

has no definition for plain real numbers but it has definition for complex numbers.

In Perl terms this means that supplying the usual Perl numbers (also known as scalars, please see perldata) as input for the trigonometric functions might produce as output results that no more are simple real numbers: instead they are complex numbers.

The `Math::Trig`

handles this by using the `Math::Complex`

package which knows how to handle complex numbers, please see Math::Complex for more information. In practice you need not to worry about getting complex numbers as results because the `Math::Complex`

takes care of details like for example how to display complex numbers. For example:

print asin(2), "\n";

should produce something like this (take or leave few last decimals):

1.5707963267949-1.31695789692482i

That is, a complex number with the real part of approximately `1.571`

and the imaginary part of approximately `-1.317`

.

(Plane, 2-dimensional) angles may be converted with the following functions.

$radians = deg2rad($degrees); $radians = grad2rad($gradians); $degrees = rad2deg($radians); $degrees = grad2deg($gradians); $gradians = deg2grad($degrees); $gradians = rad2grad($radians);

The full circle is 2 *pi* radians or *360* degrees or *400* gradians.

Saying `use Math::Trig;`

exports many mathematical routines in the caller environment and even overrides some (`sin`

, `cos`

). This is construed as a feature by the Authors, actually... ;-)

The code is not optimized for speed, especially because we use `Math::Complex`

and thus go quite near complex numbers while doing the computations even when the arguments are not. This, however, cannot be completely avoided if we want things like `asin(2)`

to give an answer instead of giving a fatal runtime error.

Jarkko Hietaniemi <*jhi@iki.fi*> and Raphael Manfredi <*Raphael_Manfredi@grenoble.hp.com*>.

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