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Mathematics 10 Online
OpenStudy (anonymous):

Integrate (sinxcosx) dx

OpenStudy (amistre64):

might want to consider what the derivative of sin or cos is ...

OpenStudy (anonymous):

hmm i did substitution but i got 2 separate answers, one is 1/2sin2x and the other is -1/2cos^2x

OpenStudy (anonymous):

* 1/2sin^2x

OpenStudy (amistre64):

sin^n (x) derives to n sin^(n-1)(x) cos(x) right?

OpenStudy (amistre64):

1/2 sin^2(x) seems appropriate to me

hartnn (hartnn):

i'd say both are correct but incomplete. 1/2 sin^2 x + c is equivalent to -1/2 cos^2x +c

OpenStudy (amistre64):

i was leading to that as well :)

hartnn (hartnn):

you can always use the identity sin^2 x + cos^2 x =1 to interchange among those 2 equivalent forms

hartnn (hartnn):

the constant you get 1/2 or -1/2 can be combined with the constant c to get another constant say C

hartnn (hartnn):

did your doubt get cleared ?

OpenStudy (anonymous):

hm i think so, then the answers are both correct, but there must be a c there which are equal to each other?

hartnn (hartnn):

the 'c' there is just to represent the constant of integration like x^2+c and x^2+1+c are equivalent functions, because the derivative of both of them is 2x so, yes, you can say both are correct, but with different constant "c" values, which does not matter

OpenStudy (anonymous):

i see, okay that makes it clear now, thanks! :D

hartnn (hartnn):

welcome ^_^

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