Käänteislukukäsite

Käänteislukukäsite, known in English as the concept of a reciprocal, refers to a number that, when multiplied by a given number, produces the multiplicative identity, which is 1. For any non-zero number 'a', its reciprocal, denoted as 1/a or a⁻¹, is the number such that a * (1/a) = 1.

The reciprocal of a fraction a/b is b/a, provided that neither a nor b is zero. For example, the reciprocal of 2/3 is 3/2, because (2/3) * (3/2) = 6/6 = 1. The reciprocal of an integer 'n' is 1/n. For instance, the reciprocal of 5 is 1/5.

The concept of a reciprocal is fundamental in arithmetic and algebra. Division can be understood as multiplication by a reciprocal. For example, dividing a number 'x' by a number 'y' (x / y) is equivalent to multiplying 'x' by the reciprocal of 'y' (x * (1/y)).

Special cases include the reciprocal of 1, which is 1 itself (1 * 1 = 1), and the reciprocal of -1, which is also -1 (-1 * -1 = 1). Zero does not have a reciprocal, as any number multiplied by zero is zero, and it's impossible to reach 1. The term 'käänteisluku' literally translates to "inverse number" in Finnish, highlighting its role in undoing multiplication.