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Category: Integration

cos-4x-cos-2x-sin-4x-cos-2x-dx-

Question Number 82954 by john santu last updated on 26/Feb/20 $$\int\:\frac{\mathrm{cos}\:\mathrm{4x}−\mathrm{cos}\:\mathrm{2x}}{\mathrm{sin}\:\mathrm{4x}−\mathrm{cos}\:\mathrm{2x}}\:\mathrm{dx}\: \\ $$ Commented by john santu last updated on 26/Feb/20 $$\mathrm{let}\:\mathrm{u}=\:\mathrm{cos}\:\mathrm{2x}\:\Rightarrow\:\mathrm{dx}\:=\:−\frac{\mathrm{du}}{\mathrm{2}\sqrt{\mathrm{1}−\mathrm{u}^{\mathrm{2}} }} \\ $$$$\Rightarrow\int\:\frac{\:\mathrm{2u}^{\mathrm{2}}…

Question-148467

Question Number 148467 by bramlexs22 last updated on 28/Jul/21 Answered by puissant last updated on 28/Jul/21 $$\mathrm{x}=\mathrm{tan}\left(\mathrm{t}\right)\Rightarrow\mathrm{dx}=\mathrm{1}+\mathrm{tan}^{\mathrm{2}} \left(\mathrm{t}\right)\mathrm{dt} \\ $$$$\mathrm{0}\leqslant\mathrm{x}\leqslant\infty\:\Rightarrow\:\mathrm{0}\leqslant\mathrm{t}\leqslant\frac{\pi}{\mathrm{2}} \\ $$$$\Rightarrow\mathrm{I}=\int_{\mathrm{0}} ^{\frac{\pi}{\mathrm{2}}} \frac{\mathrm{arctan}\left(\mathrm{tan}\left(\mathrm{t}\right)\right)}{\mathrm{1}+\mathrm{tan}^{\mathrm{2}} \left(\mathrm{t}\right)}\left(\mathrm{1}+\mathrm{tan}^{\mathrm{2}}…

Find-the-cube-root-of-z-1-

Question Number 17392 by tawa tawa last updated on 05/Jul/17 $$\mathrm{Find}\:\mathrm{the}\:\mathrm{cube}\:\mathrm{root}\:\mathrm{of}\:\:\mathrm{z}\:=\:−\:\mathrm{1} \\ $$ Answered by mrW1 last updated on 05/Jul/17 $$−\mathrm{1} \\ $$$$−\omega=\frac{\mathrm{1}}{\mathrm{2}}+\frac{\sqrt{\mathrm{3}}}{\mathrm{2}}\mathrm{i} \\ $$$$−\omega^{\mathrm{2}}…

cos-x-2-cos-x-dx-

Question Number 17377 by tawa tawa last updated on 04/Jul/17 $$\int\:\:\frac{\mathrm{cos}\left(\mathrm{x}\right)}{\mathrm{2}\:−\:\mathrm{cos}\left(\mathrm{x}\right)}\:\mathrm{dx} \\ $$ Answered by ajfour last updated on 05/Jul/17 $$\mathrm{cos}\:\mathrm{x}=\frac{\mathrm{1}−\mathrm{tan}^{\mathrm{2}} \:\left(\mathrm{x}/\mathrm{2}\right)}{\mathrm{1}+\mathrm{tan}\:^{\mathrm{2}} \left(\mathrm{x}/\mathrm{2}\right)}\:=\frac{\mathrm{2}\left(\mathrm{1}−\mathrm{t}^{\mathrm{2}} \right)}{\mathrm{1}+\mathrm{t}^{\mathrm{2}} }…