In
mathematics, a
multiplicative inverse or
reciprocal for a number
x, denoted by 1/
x or
x-1, is a number which when multiplied by
x yields the
multiplicative identity, 1. The multiplicative inverse of a
fraction a/
b is
b/
a. For the multiplicative inverse of a real number, divide 1 by the number. For example, the reciprocal of 5 is one fifth (1/5 or 0.2), and the reciprocal of 0.25 is 1 divided by 0.25, or 4. The
reciprocal function, the function
f(
x) that maps
x to 1/
x, is one of the simplest examples of a function which is its own inverse (an
involution).