If f(A) = g(B) wherever A and B are complementary angles, a function f is a cofunction of a function g in mathematics. This is a common definition for trigonometric functions. Edmund Gunter's contains the prefix "co-". Sine and cosine are examples of cofunctions (hence the "co" in "cosine"). Secant and cosecant are the same as tangent and cotangent. This is also related to versine, coversine, vercosine, covercosine, haversine, hacoversine, havercosine, hacovercosine, exsecant and excosecant.