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`int(e^(sinx))/(cos^2x)(xcos^3x-sinx) dx`A. `(x + sec x) e^(sin x) + c`B. `(x - sec x) e^(sin x) + c`C. `(x + tan x) e^(sin x) + c`D. `(x - tan x)e^(sin x) + c` |
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Answer» Correct Answer - B Let us differentiate all the options one by one to get the expression in the question whose integral is to be found. Here `xe^(sin x)` is the common term in all the options. So let us differentiate it first Let `l = xe^(sin x)` `rArr (dl)/(dx) = e^(sin x) [ x cos x + 1]` `rArr (dl)/(dx) = (e^(sin x))/(cos^(2)x) [x cos^(3) x + cos^(2) x]` Let `m = sec xe^(sin x)` `rArr (dm)/(dx) = sec xe^(sin x). cos x + e^(sin x) sec x tan x` `rArr (dm)/(dx) = e^(sin x) [1 + (sin x)/(cos^(2) x)]` `rArr (dm)/(dx) = (e^(sin x))/(cos^(2)x) [cos^(2) x + sin x]` Differentiation of option (a) is `= (e^(sin x))/(cos^(2) x) [x cos^(3) x + cos^(2) x + cos^(2) x + sin x]` `= (e^(sin x))/(cos^(2)x) [x cos^(3) x + 2 cos^(2) x + sin x]` Differentiation of option (b) is `= (e^(sin x))/(cos^(2) x) [x cos^(3) x + cos^(2) x - cos^(2) x - sin x]` `= (e^(sin x))/(cos^(2)x) [x cos^(3) x - sin x]` `:.` Option (b) is correct |
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