1. Plural of cofunction. In trigonometry, pairs of trigonometric functions whose values are equal when their arguments are complementary angles (e.g., sine and cosine, tangent and cotangent).
Usage: mathematics; trigonometry

Examples

• Sine and cosine are cofunctions because sin(θ) = cos(90° − θ).
• The relationship between cofunctions helps simplify trigonometric identities.
• Students learn that tangent and cotangent are cofunctions in their geometry class.
• Cofunctions are useful for converting between different trigonometric expressions.