Question

What is the cofunction of cos 2pi/ 9

Answer 1

The cofunction of cos is sin(90-x)

90 degrees is equal to PI/2

The cofunction becomes sin(PI/2 - 2PI/9)

Rewrite both fractions to have a common denominator:

PI/2 = 9PI/18

2PI/9 = 4PI/18

Now you have sin(9PI/18 - 4PI/18)

Simplify:

Sin(5PI/18)