1. In trigonometry, either of two functions whose values are complementary; specifically, sine and cosine, or tangent and cotangent, or secant and cosecant.
Usage: mathematics; trigonometry

Examples

• Sine and cosine are cofunctions because sin(θ) = cos(90° − θ).
• The cofunction identity relates tangent and cotangent.
• Students learn that cofunctions have equal values at complementary angles.
• In trigonometry, secant and cosecant are cofunctions of each other.