Cofunctions in trigonometry are function pairs like sine and cosine
Examples:
sin(π/2 - x) = cos(x), cos(π/2 - x) = sin(x), tan(π/2 - x) = cot(x), and cot(π/2 - x) = tan(x)
Purpose:
The cofunction identities show the relationship between sine, cosine, tangent, cotangent, secant, and cosecant. The value of an angle's trig function equals the value of the angle's complement's cofunction