具体步骤如下图所示:
∫sectdt
=∫1/cost dt
=∫1/[cos²(t/2)-sin²(t/2) dt
=∫sec²(t/2) /[1-tan²(t/2)]dt
=∫2/[1-tan²(t/2)] dtan(t/2)
=∫{1/[1+tan(t/2)] -1/[tan(t/2)-1]}dtan(t/2)
=㏑|[1+tan(t/2)]/[tan(t/2)-1]| +C
=㏑|[sin(t/2)+cos(t/2)]/[sin(t/2)-cos(t/2)]|+C
=㏑|(1+sint)/cost| +C
=㏑|sect+tant| +C
可以记住