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Mathematics 15 Online
OpenStudy (anonymous):

help?

OpenStudy (anonymous):

let me write!

OpenStudy (anonymous):

\[\int\limits sinx cosx dx\]

OpenStudy (anonymous):

i give u choices wait..

OpenStudy (anonymous):

\[ 1.\frac{ \sin^2x }{ 2 } 2. \frac{ \cos^2x }{ 2}\]

OpenStudy (anonymous):

cos^2x/2

OpenStudy (anonymous):

actually its sin^2x/2... sorry

OpenStudy (anonymous):

so u bring the power down, decrease the power by 1 and multiply by the derivative of sinx... do u understand that?

OpenStudy (anonymous):

in mathematical form plz..

OpenStudy (anonymous):

?

OpenStudy (anonymous):

i dont know how to explain it in a better way... think of it this way: (sinx)^2 so u have to multipy it with the derivative of wats inside the brackets after u decrease the power... do u get it now?

OpenStudy (anonymous):

it's really slow sorry for late reply

OpenStudy (anonymous):

err... m sorry, m quite bad with explaining i hope some1 else can give u hand with it

OpenStudy (anonymous):

it's okay :)

OpenStudy (anonymous):

sin x cos x = 1/2 * sin(2x) so just integrate 1/2 sin (2x)

OpenStudy (anonymous):

you should get -1/2 cos^2 (x)

OpenStudy (anonymous):

alternatively you could let u = sin x, and du = cos x. or let u = cos x and let du = -sin x.. so many ways which way do you prefer

OpenStudy (anonymous):

answer should be sin^2x/2...!

OpenStudy (anonymous):

?

OpenStudy (anonymous):

\[\int\limits_{}^{} \sin x * \cos x dx = \frac{ \sin^{2} x }{ 2 }\] ?

OpenStudy (anonymous):

yeah

OpenStudy (anonymous):

ah ok well i guess they only differ by a constant \[\frac{ \sin^{2}x }{ 2 } = \frac{ -\cos^{2} x }{ 2 } + \frac{ 1 }{ 2 }\] there are many answers to this question

OpenStudy (anonymous):

thanks:)

OpenStudy (anonymous):

u substitution u=sinx du=cosx dx integral = udu integrate that and you get (u^2)/2 Insert sinx back in for u and you get [sin^2 (x)] / 2

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