WHAT IS INDENTY An identity is an equality relation A = B, such that A and B contain some variables and give the same result when the variables are substituted by any values (usually ). In other words, A = B is an identity if A and B define the same functions. This means that an identity is an equality between functions that are differently defined. For example (x + y)2  =  x2 + 2xy + y2and cos2(x) + sin2(x) = 1 are identities. Identities were sometimes indicated by the triple bar symbol ≡ instead of the equals sign =, but this is no longer a common usage

3. An identity is an equality relation A = B, such that A and B contain
some variables and give the same result when the variables are
substituted by any values (usually ). In other words, A = B is an
identity if A and B define the same functions. This means that
an identity is an equality between functions that are differently
defined. For example
(x + y)2 = x2 + 2xy + y2and cos2(x) + sin2(x) = 1 are identities.
Identities were sometimes indicated by the triple bar symbol ≡
instead of the equals sign =, but this is no longer a common usage.