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Question-159597




Question Number 159597 by mathlove last updated on 19/Nov/21
Answered by mr W last updated on 19/Nov/21
(((sin^(2014)  x sin (2014x))/(2014)))′  =((2014 sin^(2013)  x cos x sin (2014x)+sin^(2014) x×2014 cos (2014x))/(2014))  =sin^(2013)  x(cos x sin (2014x)+sin x cos (2014x))  =sin^(2013)  x sin (2014x+x)  =sin^(2013)  x sin (2015x)  ⇒∫sin^(2013)  x sin (2015x)dx=((sin^(2014)  x sin (2014x))/(2014))+C
$$\left(\frac{\mathrm{sin}^{\mathrm{2014}} \:{x}\:\mathrm{sin}\:\left(\mathrm{2014}{x}\right)}{\mathrm{2014}}\right)' \\ $$$$=\frac{\mathrm{2014}\:\mathrm{sin}^{\mathrm{2013}} \:{x}\:\mathrm{cos}\:{x}\:\mathrm{sin}\:\left(\mathrm{2014}{x}\right)+\mathrm{sin}\:^{\mathrm{2014}} {x}×\mathrm{2014}\:\mathrm{cos}\:\left(\mathrm{2014}{x}\right)}{\mathrm{2014}} \\ $$$$=\mathrm{sin}^{\mathrm{2013}} \:{x}\left(\mathrm{cos}\:{x}\:\mathrm{sin}\:\left(\mathrm{2014}{x}\right)+\mathrm{sin}\:{x}\:\mathrm{cos}\:\left(\mathrm{2014}{x}\right)\right) \\ $$$$=\mathrm{sin}^{\mathrm{2013}} \:{x}\:\mathrm{sin}\:\left(\mathrm{2014}{x}+{x}\right) \\ $$$$=\mathrm{sin}^{\mathrm{2013}} \:{x}\:\mathrm{sin}\:\left(\mathrm{2015}{x}\right) \\ $$$$\Rightarrow\int\mathrm{sin}^{\mathrm{2013}} \:{x}\:\mathrm{sin}\:\left(\mathrm{2015}{x}\right){dx}=\frac{\mathrm{sin}^{\mathrm{2014}} \:{x}\:\mathrm{sin}\:\left(\mathrm{2014}{x}\right)}{\mathrm{2014}}+{C} \\ $$
Commented by mathlove last updated on 20/Nov/21
thenks master
$${thenks}\:{master} \\ $$
Commented by infinityaction last updated on 25/Apr/22

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