Musical instruments that start with the letter I include the igil, ipu, Irish uillean, Irish bouzouki, ichigenkin, inci, iya, itotele and istarski mih. The instruments originate from countries ranging from Cuba and Ireland to Croatia, Japan and the Philippines.
Bessel's functions are often used in acoustics for describing circular membranes behaviour (exploited by most of the musical instruments). They are the solutions of the wave equations using polar coordinates. Set the properties of the membrane Bessel's functions describe the vibrational modes of the membrane.
The value arguments of the IS functions are not converted. For example, in most other functions where a number is required, the text value 19 is converted to the number 19. However, in the formula ISNUMBER(19), 19 is not converted from a text value, and the IsNumber(Object) function returns false. The IS functions are useful in formulas for testing the outcome of a calculation. When combined with the IF function, they provide a method for locating errors in formulas.