Question Number 73608 by mathocean1 last updated on 13/Nov/19
$$\:\mathrm{determiner} \\ $$$$\:\mathrm{la}\:\mathrm{valeur}\:\mathrm{exacte}\:\mathrm{de}\:\mathrm{sin}\left(\frac{\mathrm{85}\Pi}{\mathrm{4}}\right) \\ $$$$ \\ $$
Commented by mathmax by abdo last updated on 13/Nov/19
$${sin}\left(\frac{\mathrm{85}\pi}{\mathrm{4}}\right)\:={sin}\left(\mathrm{20}\pi\:+\frac{\mathrm{5}\pi}{\mathrm{4}}\right)\:={sin}\left(\frac{\mathrm{5}\pi}{\mathrm{4}}\right)\:={sin}\left(\pi\:+\frac{\pi}{\mathrm{4}}\right)\:\:\left(\mathrm{20}\pi\:{is}\:{period}\right) \\ $$$$=−{sin}\left(\frac{\pi}{\mathrm{4}}\right)=−\frac{\sqrt{\mathrm{2}}}{\mathrm{2}} \\ $$
Commented by kaivan.ahmadi last updated on 13/Nov/19
$${sin}\left(\mathrm{21}\pi+\frac{\pi}{\mathrm{4}}\right)={sin}\left(\pi+\frac{\pi}{\mathrm{4}}\right)=−{sin}\left(\frac{\pi}{\mathrm{4}}\right)=−\frac{\sqrt{\mathrm{2}}}{\mathrm{2}} \\ $$
Commented by mathocean1 last updated on 14/Nov/19
$$\mathrm{thank}\:\mathrm{you}\:\mathrm{sir} \\ $$
Commented by mathocean1 last updated on 14/Nov/19
$$\mathrm{thank}\:\mathrm{you}\:\mathrm{sir} \\ $$
Commented by mathmax by abdo last updated on 14/Nov/19
$${you}\:{are}\:{welcome}. \\ $$