1.
If ∫sec⁡2xcosec⁡4x dx=−13cot⁡3x+ktan⁡x−2cot⁡x+C\int \sec^2 x \cosec^4 x\,dx = -\frac13\cot^3 x + k\tan x - 2\cot x + C, then k=k=