Question

Integral of sinx sin2x

Answer 1

$\bf HELLO \: \: DEAR$

$\bf \int sinxsin2x .dx$

$\boxed {\bf Now,}$


$\bf \int sinx(2sinxcosx).dx$


$\to \bf 2\int sin^{2}x. cosx. dx$


$\bf let \: \: u = sinx \\ \\ \bf du/dx = cosx \\ \\ \bf \: du = cosx.dx$


$\to \bf 2\int u^{2} .du$


$\to \bf 2u^{3}/3 + C$

$\underline { \bf hence}$

$\bf \int sinxsin2x. dx = 2sin^{3}x/3 + C$



$\it {\underline {\bf I \: \: HOPE \: \: ITS \: \: HELP \: \: YOU \: \: DEAR, \: \: THANKS}}$