Question

Which additional identity-function relation is valid whenever the composition is defined?

Options

• \(I_B\circ f=f+I_B\)

• \(I_B\circ f=I_B\)

• \(I_B\circ f=f^{-1}\)

• \(I_B\circ f=f\)

Answer 1

The identity function \(I_B\) leaves every element of \(B\) unchanged. Therefore, applying \(I_B\) after \(f\) gives \(I_B\circ f=f\), whenever defined.