## Precalculus (6th Edition) Blitzer

The additive identity states that if a number is added to the real number, then the result is the same real number. We know that the number zero is an additive identity. Now, for the example: $2+0=2$ And the multiplicative identity states that when a number is multiplied by 1, the result is the same original number. Let us take an example: $2\times 1=2$ The trigonometric identities refer to the equalities that include trigonometric functions and are true for each and every value of the occurring variables, where both sides of the equality are defined. Hence, the word identity is used in various ways in additive identity, multiplicative identity, and trigonometric identity.