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Category: Integration

Question-128346

Question Number 128346 by Ahmed1hamouda last updated on 06/Jan/21 Answered by MJS_new last updated on 06/Jan/21 x24x2+1dx=$$\:\:\:\:\:\left[{t}=\mathrm{2}{x}+\sqrt{\mathrm{4}{x}^{\mathrm{2}} +\mathrm{1}}\:\rightarrow\:{dx}=\frac{\sqrt{\mathrm{4}{x}^{\mathrm{2}} +\mathrm{1}}}{\mathrm{2}\left(\mathrm{2}{x}+\sqrt{\mathrm{4}{x}^{\mathrm{2}} +\mathrm{1}}\right)}{dt}\right] \

cos-pi-7-cos-2pi-7-cos-3pi-7-

Question Number 128285 by john_santu last updated on 06/Jan/21 cos(π7)cos(2π7)+cos(3π7)=? Answered by liberty last updated on 06/Jan/21 letφ=cos(π7)cos(2π7)+cos(3π7)φ=cos(π7)+cos(3π7)+cos(5π7)$$\:\Rightarrow\mathrm{2}\varphi\mathrm{sin}\:\mathrm{t}\:=\:\mathrm{2sin}\:\mathrm{t}\:\mathrm{cos}\:\mathrm{t}\:+\:\mathrm{2sin}\:\mathrm{t}\:\mathrm{cos}\:\mathrm{3t}+\mathrm{2sin}\:\mathrm{tcos}\:\mathrm{5t} \