Question Number 181756 by Mastermind last updated on 29/Nov/22
$$\mathrm{Without}\:\mathrm{using}\:\mathrm{calculator},\:\mathrm{what}\:\mathrm{is}\:\mathrm{the} \\ $$$$\mathrm{value}\:\mathrm{of}\:\mathrm{Cos}\left(\frac{\mathrm{7}\pi}{\mathrm{6}}\right)? \\ $$$$ \\ $$$$. \\ $$
Answered by a.lgnaoui last updated on 29/Nov/22
$$\mathrm{cos}\:\left(\frac{\mathrm{7}\pi}{\mathrm{6}}\right)=\mathrm{cos}\:\left(\frac{\mathrm{6}\pi+\pi}{\mathrm{6}}\right)=−\mathrm{cos}\left(\frac{\pi}{\mathrm{6}}\right)=\frac{−\sqrt{\mathrm{3}}}{\mathrm{2}}\: \\ $$
Answered by CElcedricjunior last updated on 29/Nov/22
$$\boldsymbol{{cos}}\left(\frac{\mathrm{7}\boldsymbol{\pi}}{\mathrm{6}}\right)=\boldsymbol{{cos}}\left(\boldsymbol{\pi}+\frac{\boldsymbol{\pi}}{\mathrm{6}}\right)=−\boldsymbol{{cos}}\frac{\boldsymbol{\pi}}{\mathrm{6}}=−\frac{\sqrt{\mathrm{3}}}{\mathrm{2}} \\ $$$$.====================== \\ $$$$........{le}\:{celebre}\:{cedric}\:{junior}.......... \\ $$$$=================== \\ $$