Sum and Difference of Two Angles
Go to the derivation of sum and difference of two angles if you want information on where these formulas came from.
1. sin(α+β)=sinαcosβ+cosαsinβ
2. sin(α−β)=sinαcosβ−cosαsinβ
3. cos(α+β)=cosαcosβ−sinαsinβ
4. cos(α−β)=cosαcosβ+sinαsinβ
5. tan(α+β)=tanα+tanβ1−tanαtanβ
6. tan(α−β)=tanα−tanβ1+tanαtanβ