Inverse cosecant function

Use only in the MuPAD Notebook Interface.

This functionality does not run in MATLAB.




arccsc(x) represents the inverse of the cosecant function.

The angle returned by this function is measured in radians, not in degrees. For example, the result π represents an angle of 180o.

arccsc is defined for complex arguments.

Floating-point values are returned for floating-point arguments. Floating-point intervals are returned for interval arguments. Unevaluated function calls are returned for most exact arguments.

If the argument is a rational multiple of I, the result is expressed in terms of hyperbolic functions. See Example 2.

MuPAD® rewrites arccsc as arccsc(x) = arcsin(1/x).

The inverse cosecant functions is multivalued. The MuPAD arccsc function returns values on the main branch. The branch cut is the real interval (- 1, 1). Thus, arccsc returns values, such that y = arccsc(x) satisfies π2(y)π2,y0 for any finite complex x.

The arccsc function returns explicit values for arguments that are certain rational multiples of π. For these values, the inverse functions return an appropriate rational multiple of π on the main branch. See Example 3.

The values jump when the arguments cross a branch cut. See Example 4.

The float attributes are kernel functions. Thus, floating-point evaluation is fast.

Environment Interactions

When called with a floating-point argument, arccsc is sensitive to the environment variable DIGITS which determines the numerical working precision.


Example 1

Call arccsc with the following exact and symbolic input arguments:

arccsc(1), arccsc(1/sqrt(2)), arccsc(5 + I),
arccsc(1/3), arccsc(I), arccsc(-1)

arccsc(-x), arccsc(x + 1), arccsc(1/x)

Floating-point values are computed for floating-point arguments:

arccsc(0.1234), arccsc(5.6 + 7.8*I), arccsc(1.0/10^20)

Floating-point intervals are computed for interval arguments:

arccsc(-2...-1), arccsc(1...5)

Note that certain types of input lead to severe overestimation, sometimes returning the whole image set of the function in question:


Example 2

Arguments that are rational multiples of I are rewritten in terms of hyperbolic functions:

arccsc(5*I), arccsc(5/4*I), arccsc(-3*I)

For other complex arguments unevaluated function calls without simplifications are returned:

arccsc(1/2^(1/2) + I), arccsc(1 - 3*I)

Example 3

Some special values are implemented:

arccsc(sqrt(2)), arccsc(4/(5^(1/2) - 1)), arccsc(2/3^(1/2))

Such simplifications occur for arguments that are trigonometric images of rational multiples of π:

csc(9/10*PI), arccsc(csc(9/10*PI))

Example 4

The values jump when crossing a branch cut:

arccsc(0.5 + I/10^10), arccsc(0.5 - I/10^10)

On the branch cut, the values of arccsc coincide with the limit "from above" for real arguments 0 < x < 1:

limit(arccsc(0.5 - I/n), n = infinity);
limit(arccsc(0.5 + I/n), n = infinity);

The values coincide with the limit "from below" for real -1 < x < 0:

limit(arccsc(-0.5 - I/n), n = infinity);
limit(arccsc(-0.5 + I/n), n = infinity);

Example 5

The inverse cosecant function can be rewritten in terms of the logarithm function with complex arguments:

rewrite(arccsc(x), ln)

Example 6

diff, float, limit, taylor, series, and other system functions handle expressions involving the inverse trigonometric functions:

diff(arccsc(x^2), x), float(arccsc(3)*arctan(5 + I))

limit(arccsc(1 + sin(x)/x), x = 0)

taylor(arccsc(1/x), x = 0)

series(arccsc(x), x = 0, Right)

Return Values

Arithmetical expression or floating-point interval.

Overloaded By


See Also

MuPAD Functions

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