两角及公式:
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)