∫secxdx推导过程
∫secxdx
=∫secx(tanx+secx)dx/(tanx+secx)
=∫(secxtanx+secx)dx/(tanx+secx)
=∫d(secx+tanx)/(secx+tanx)
=ln|secx+tanx|+C
Dx sin x=cos x
cos x = -sin x
tan x = sec2 x
cot x = -csc2 x
sec x = sec x tan x
csc x = -csc x cot x
sin x dx = -cos x + C
cos x dx = sin x + C
tan x dx = ln |sec x | + C
cot x dx = ln |sin x | + C