The Cosecant is the reciprocal of the Sine.
Therefore, for the simple rightangled triangle below, the cosecant of the angle θ is equal to the hypotenuse, h, divided by the opposite side, o.
I.e. for the triangle above,
The trig. ratios are discussed further on the Wikipedia Trigonometric Ratios PageThe Excel Csc function calculates the cosecant of a given angle.
Note: the Csc function was only introduced in Excel 2013 and so is not available in earlier versions of Excel.
The syntax of the function is:
Where the number argument is the angle (in radians) that you want to calculate the cosecant of. This must be between 2^27 and +2^27.
If the supplied number argument is equal to 0, the Csc function returns the #DIV/0! error.
Converting from Degrees to Radians
If your angle is in degrees, you will need to convert it into radians before supplying it to the Csc function. This can be done using the Excel Radians function:
The following spreadsheet shows the Excel Csc Function, used to calculate the Cosecant of four different angles:
Formulas:
 Results:

Note that, in the above spreadsheet:
Further details and examples of the Excel Csc function are provided on the Microsoft Office website.
If you get an error from the Excel Csc function, this is likely to be one of the following:
#DIV/0!    Occurs if the supplied number is equal to zero. 
#NUM!    Occurs if the supplied number is less than 2^27 or is greater than 2^27. 
#VALUE!    Occurs if the supplied number is not recognised as a numeric value. 