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SuckMyEsophagusBest ResponseYou've already chosen the best response.0
Let u = cos x du = sin x dx then, "integral [u^3 du]" or " integral [u^3 du] " = (u^4)/4 + C = (cos^4 x)/4 + C
 one year ago

kaiz122Best ResponseYou've already chosen the best response.0
i have a question, sin x is in the denominator, how does it become the du then?
 one year ago

SuckMyEsophagusBest ResponseYou've already chosen the best response.0
Because everything is substituted and then flipped :)
 one year ago

kaiz122Best ResponseYou've already chosen the best response.0
i tried checking it by differentiation, then i got (cos^3x )(sinx)
 one year ago

SuckMyEsophagusBest ResponseYou've already chosen the best response.0
Are you using your calculator?
 one year ago

SuckMyEsophagusBest ResponseYou've already chosen the best response.0
You can integrate this directly, just notice that differentiating cos^4(x) gives you 4cos^3(x)sin(x) by the chain rule. Hence the integral of cos^3(x)sin(x) is 1/4 cos^4(x)
 one year ago

kaiz122Best ResponseYou've already chosen the best response.0
i still don't get it, how does sin x in the denominator becomes du? dx/sinx is not equal to sinx dx right.
 one year ago

SuckMyEsophagusBest ResponseYou've already chosen the best response.0
No their not the equal
 one year ago

kaiz122Best ResponseYou've already chosen the best response.0
@saifoo.khan can you please help me here
 one year ago

AravindGBest ResponseYou've already chosen the best response.0
use @AravindG if u have any integration qns in future
 one year ago
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