Definition:Cofunction

Definition

Let $f$ be a trigonometric function

Then $g$ is a cofunction of $f$ if and only if:

$\forall x \in \R: \map g x = \map f {90 \degrees - x}$

That is, such that the image of $x$ under $f$ equals the image of the complement of $x$ under $g$.

Also see

• Results about cofunctions can be found here.

Sources

• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): cofunctions
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): cofunctions