In: Math
The integral ∫sec2x/(sec x + tan x)9/2 dx equals (for some arbitrary constant k)
Let I = ∫ sec²x/(sec x + tan x)^(9/2) dx
= ∫sec x .sec x. /(sec x + tan x)^(9/2) dx
Put sec x + tan x = t
sec x tan x + sec²x dx = dt
sec x (tan x + sec x) = dt
sec – tan x = 1/t
2 sec x = t + 1/t
sec x = ½ (t + 1/t)
So I = ½ ∫[(t + 1/t)dt/t]/t^(9/2)
= ½ ∫ [t^(-9/2) + t^(-13/2)] dt
= ½ [ (-2/7)t^(-7/2) – (2/11)t^(-11/2)]+ C
= -[ (t^(-7/2)/7) + t^(-11/2)/11] + C
= -[ (sec x + tan x)^(-7/2)/7 + (sec x + tan x)^(-11/2)/11]+ C
-[ (sec x + tan x)-7/2/7 + (sec x + tan x)-11/2/11]+ C