sin(a+b)=sinAcosB+sinBcosA
sin(a-b)=sinAcosB-sinBcosA
cos(a+b)=cosAcosB-sinAsinB
cos(a-b)=cosAcosB+sinAsinB
(tanA)2+1=(secA)2=1÷(cosA)2
(cotA)2+1=(cscA)2=1÷(sinA)2
1.y'+sin(x-y)=sin(x+y)
解:
1.∫secxdx=ln|secx+tanx|+c
2.∫cscxdx=ln|cscx-cotx|+c
3.∫I÷√a2+x2dx=ln|(x+√a2+x2)+c
