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.
Functions. A function is a rule that applies to a variable. Let's say everybody (except your friend) did poorly on the test, and your teacher decides to use a curve to change all the grades. The rule he uses for the curve is to bump everybody's grade up by 3 points.