The so-called "inductive formula" is to simplify the original relatively complicated formula that is not conducive to calculation into an easy and relatively good solution formula through these intermediate formulas, thus completing the calculation requirements. These formulas played an inductive role in this process, hence the name "inductive formula".

The main inductive formulas are as follows:

sin(π-α) = sin α

cos(π-α) = - cos α

……

sin(-α) =cos α

cos(-α) =-sin α

……

Sine (2π-α)=- Sine α

cos(2π-α) =cos α