Indefinite IntegrationHard
Question
cosx cos3x dx equals-Options
A.
(sin 4x + 2 sin 2x) + c
(sin 4x + 2 sin 2x) + c B.(sin 4x − 2 sin 2x) + c
(sin 4x − 2 sin 2x) + c C.sin x sin 3x + c
sin x sin 3x + c D.None of these