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Question Number 74130 by mathocean1 last updated on 19/Nov/19
hello] help me to solve it in ]−Π;Π]×]−Π;Π] please   { ((x−y=(Π/6))),((cosx−(√3)cosy=−(1/2))) :}
$$\left.\mathrm{h}\left.\mathrm{e}\left.\mathrm{l}\left.\mathrm{l}\left.\mathrm{o}\right]\:\mathrm{help}\:\mathrm{me}\:\mathrm{to}\:\mathrm{solve}\:\mathrm{it}\:\mathrm{in}\:\right]−\Pi;\Pi\right]×\right]−\Pi;\Pi\right]\:\mathrm{please} \\ $$$$\begin{cases}{\mathrm{x}−\mathrm{y}=\frac{\Pi}{\mathrm{6}}}\\{\mathrm{cosx}−\sqrt{\mathrm{3}}\mathrm{cosy}=−\frac{\mathrm{1}}{\mathrm{2}}}\end{cases} \\ $$
Answered by Tanmay chaudhury last updated on 19/Nov/19
cos((π/6)+y)−(√3) cosy=((−1)/2)  ((√3)/2)cosy−(1/2)siny−(√3) cosy=((−1)/2)  ((−1)/2)siny−((√3)/2)cosy=((−1)/2)  (1/2)siny+((√3)/2)cosy=(1/2)  sin((π/3)+y)=sin(π/6)  (π/3)+y=(π/6)→y=−(π/6)  so x=y+(π/6)→x=0  sin((π/3)+y)=sin(π/6)=sin(π−(π/6))  (π/3)+y=((5π)/6)→y=((5π)/6)−((2π)/6)=(π/2)  x=(π/6)+y→x=(π/6)+((3π)/6)=((4π)/6)
$${cos}\left(\frac{\pi}{\mathrm{6}}+{y}\right)−\sqrt{\mathrm{3}}\:{cosy}=\frac{−\mathrm{1}}{\mathrm{2}} \\ $$$$\frac{\sqrt{\mathrm{3}}}{\mathrm{2}}{cosy}−\frac{\mathrm{1}}{\mathrm{2}}{siny}−\sqrt{\mathrm{3}}\:{cosy}=\frac{−\mathrm{1}}{\mathrm{2}} \\ $$$$\frac{−\mathrm{1}}{\mathrm{2}}{siny}−\frac{\sqrt{\mathrm{3}}}{\mathrm{2}}{cosy}=\frac{−\mathrm{1}}{\mathrm{2}} \\ $$$$\frac{\mathrm{1}}{\mathrm{2}}{siny}+\frac{\sqrt{\mathrm{3}}}{\mathrm{2}}{cosy}=\frac{\mathrm{1}}{\mathrm{2}} \\ $$$${sin}\left(\frac{\pi}{\mathrm{3}}+{y}\right)={sin}\frac{\pi}{\mathrm{6}} \\ $$$$\frac{\pi}{\mathrm{3}}+{y}=\frac{\pi}{\mathrm{6}}\rightarrow{y}=−\frac{\pi}{\mathrm{6}} \\ $$$${so}\:{x}={y}+\frac{\pi}{\mathrm{6}}\rightarrow{x}=\mathrm{0} \\ $$$${sin}\left(\frac{\pi}{\mathrm{3}}+{y}\right)={sin}\frac{\pi}{\mathrm{6}}={sin}\left(\pi−\frac{\pi}{\mathrm{6}}\right) \\ $$$$\frac{\pi}{\mathrm{3}}+{y}=\frac{\mathrm{5}\pi}{\mathrm{6}}\rightarrow{y}=\frac{\mathrm{5}\pi}{\mathrm{6}}−\frac{\mathrm{2}\pi}{\mathrm{6}}=\frac{\pi}{\mathrm{2}} \\ $$$${x}=\frac{\pi}{\mathrm{6}}+{y}\rightarrow{x}=\frac{\pi}{\mathrm{6}}+\frac{\mathrm{3}\pi}{\mathrm{6}}=\frac{\mathrm{4}\pi}{\mathrm{6}} \\ $$$$ \\ $$$$ \\ $$$$ \\ $$$$ \\ $$$$ \\ $$

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