两角和公式:
1.sin(A+B)=sinAcosB+cosAsinB
2.sin(A-B)=sinAcosB-cosAsinB
3.cos(A+B)=cosAcosB-sinAsinB
4.cos(A-B)=cosAcosB+sinAsinB
5.tan(A+B)=(tanA+tanB)/(1-tanAtanB)
6.tan(A-B)=(tanA-tanB)/(1+tanAtanB)
7.tanA+tanB=tan(A+B)(1-tanAtanB)
8.tanA-tanB=tan(A-B)(1+tanAtanB)