Question Number 47566 by tanmay.chaudhury50@gmail.com last updated on 11/Nov/18
$$\int{sin}\mathrm{51}{x}\left({sinx}\right)^{\mathrm{49}} {dx} \\ $$
Answered by Smail last updated on 12/Nov/18
$${A}=\int{sin}\left(\mathrm{50}{x}+{x}\right){sin}^{\mathrm{49}} \left({x}\right){dx} \\ $$$$=\int\left({sin}\left(\mathrm{50}{x}\right){cosx}+{cos}\left(\mathrm{50}{x}\right){sin}\left({x}\right)\right){sin}^{\mathrm{49}} \left({x}\right){dx} \\ $$$$=\int\left({sin}\left(\mathrm{50}{x}\right){cos}\left({x}\right){sin}^{\mathrm{49}} \left({x}\right)+{cos}\left(\mathrm{50}{x}\right){sin}^{\mathrm{50}} \left({x}\right)\right){dx} \\ $$$$=\int\left({sin}\left(\mathrm{50}{x}\right)\left(\frac{\mathrm{1}}{\mathrm{50}}{sin}^{\mathrm{50}} {x}\right)'+\left(\frac{\mathrm{1}}{\mathrm{50}}{sin}\left(\mathrm{50}{x}\right)\right)'{sin}^{\mathrm{50}} \left({x}\right)\right) \\ $$$${A}=\frac{\mathrm{1}}{\mathrm{50}}{sin}\left(\mathrm{50}{x}\right){sin}^{\mathrm{50}} {x} \\ $$
Answered by tanmay.chaudhury50@gmail.com last updated on 12/Nov/18
$$\int{sin}\left(\mathrm{50}+\mathrm{1}\right){x}\left({sinx}\right)^{\mathrm{49}} {dx} \\ $$$$\int\left[{sin}\mathrm{50}{xcosx}+{cos}\mathrm{50}{xsinx}\right]\left({sinx}\right)^{\mathrm{49}} {dx} \\ $$$$\int{sin}\mathrm{50}{xcosx}\left({sinx}\right)^{\mathrm{49}} +{cos}\mathrm{50}{x}\left({sinx}\right)^{\mathrm{50}} {dx} \\ $$$$\frac{\mathrm{1}}{\mathrm{50}}\int{sin}\mathrm{50}{x}×\mathrm{50}{cosx}\left({sinx}\right)^{\mathrm{49}} +\mathrm{50}{cos}\mathrm{50}{x}\left({sinx}\right)^{\mathrm{50}} {dx} \\ $$$$\frac{\mathrm{1}}{\mathrm{50}}\int\left[{sin}\mathrm{50}{x}×\frac{{d}}{{dx}}\left\{\left({sinx}\right)^{\mathrm{50}} \right\}+\left({sinx}\right)^{\mathrm{50}} ×\frac{{d}}{{dx}}\left({sin}\mathrm{50}{x}\right)\right]{dx} \\ $$$$\frac{\mathrm{1}}{\mathrm{50}}\int\frac{{d}}{{dx}}\left\{{sin}\mathrm{50}{x}×\left({sinx}\right)^{\mathrm{50}} \right\}{dx} \\ $$$$\frac{\mathrm{1}}{\mathrm{50}}×\left\{{sin}\mathrm{50}{x}×\left({sinx}\right)^{\mathrm{50}} \right\}+{c} \\ $$