what is "cos (pi\2 - a) "? equil to? i want it to be define

Question

plz i can not type pi alpha sign , idk how to type , i know it is equil to sina but i need to know why it is equil to sina ? i need to know

Answer 1

This is called a "Cofunction Formula."

cos(π/2 - α) = sin α

For example, cos(π/2 - 30) = sin 30

cos(90-30) = sin 30

cos 60 = sin 30

1/2 = 1/2