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(Sec[a*x]^3*(3*Sin[a*x] + Sin[3*a*x]))/6

Integrate[a*Sec[a*x]^4, x] ==
(Sec[a*x]^3*(3*Sin[a*x] + Sin[3*a*x]))/6 

                    4
Integrate[a Sec[a x] , x] == 

        3
Sec[a x]  (3 Sin[a x] + Sin[3 a x])
-----------------------------------
                 6
Time to compute: 0.01 second
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