folosim urmatoarele formule trigonometrice
sin([tex] \frac{ \pi}{2} [/tex]-x)=cos(x) >> sin (90-80)= cos 80
cos(2[tex] \pi [/tex]-x)= cos (x) >> cos (360-10)= cos 10
tg(2[tex] \pi [/tex]-x)=-tgx >> tg(360-170)=-tg(170)
ctg(2[tex] \pi [/tex]-x)= ctg (x) >> ctg (360-80)= ctg 80
dupa ce 3 dintre ele se reduc ramane sus ctg80 iar jos tg 80 iar raportul lor va fi 1
