Category: Trigonometry

Question Number 129712 by liberty last updated on 18/Jan/21 Commented by bemath last updated on 18/Jan/21 $$\mathrm{edit}\mathrm{the}\mathrm{last}\mathrm{line}\equiv \frac{3-0+\frac{3}{4}-\frac{3}{8}}{1-0-\frac{3}{4}+\frac{1}{8}}=9$$ Commented by liberty last updated on…

Question Number 129360 by bramlexs22 last updated on 15/Jan/21 $$\{\begin{array}{l}\sin a+\sin b=\frac{1}{3}\\ \cos a+\cos b=\frac{5}{3}\end{array}$$$${\cos }^2(a+b)=?$$ Commented by bramlexs22 last updated on 15/Jan/21 $$\mathrm{nice}\mathrm{trigonometry}$$…

Question Number 63703 by kaivan.ahmadi last updated on 07/Jul/19 $${sin}^{3}x+{cos}^{3}x=1-\frac{1}{2}sin2x:x\in [0,2\pi ].$$$$findx$$ Commented by Prithwish sen last updated on 08/Jul/19 $$\left(\mathrm{sinx}\:+\:\mathrm{cosx}\:\right)\:\left(\mathrm{1}−\frac{\mathrm{1}}{\mathrm{2}}\mathrm{sin2x}\right)\:−\left(\mathrm{1}−\frac{\mathrm{1}}{\mathrm{2}}\mathrm{sin2x}\right)=\mathrm{0}…

Question Number 129233 by MrJoe last updated on 14/Jan/21 $$provethat$$$$sin3x=2cos\left(\frac{3x}{2}\right)sin\left(\frac{3x}{2}\right)$$ Commented by MrJoe last updated on 15/Jan/21 $$then$$$${if}\:{sin}\left(\mathrm{3}{x}\right)={sin}\left[\mathrm{2}\left(\frac{\mathrm{3}{x}}{\mathrm{2}}\right)\right] \…

Question Number 63693 by Rio Michael last updated on 07/Jul/19 $$findthegeneralsolutionfor$$$$sin5\theta +sin3\theta =1$$ Commented by Prithwish sen last updated on 07/Jul/19 $$\mathrm{sin5}\theta+\mathrm{sin3}\theta=\mathrm{1} \…