∫ sec x dx = ln |sec x + tan x| + C       or          ∫ sec x dx = ln | tan [ (x/2) + (π/4) ] | + C.

∫ sec x dx = ln |sec x + tan x| + C or ∫ sec x dx = ln | tan [ (x/2) + (π/4) ] | + C.

*∫ sec x dx = ln | secx + tanx | + c  [OR] *∫ sec x dx = (1/2) ln | (1 + sin x) / (1 - sin x) | + c [OR] *∫ sec x dx = ln | tan [ (x/2) + (π/4) ] | + c