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Folosind formulele de reducere la primul cadran,demonstrati identitățile :a) 2cos ori (pi supra 2 - x) ori sin (pi supra 2 - x)) ori tg(pi -x) totul supra ctg (pi supra 2 +x) ori sin (pi -x) ori cos (2 pi - x) =2 :b) ctg (3pi supra 2 - x) sin (x-pi supra 2)+tg (pi +x) cos (pi + x) cos (2 pi - x) =0: c) sin (pi supra 2 - x) +sin (pi supra 2 +x) +2 cos (pi - x) =0.

Răspuns :

Salut,

[tex]\dfrac{2cos\left(\dfrac{\pi}2-x\right)\cdot sin\left(\dfrac{\pi}2-x\right)\cdot tg\left(\pi-x\right)}{ctg\left(\dfrac{\pi}2+x\right)\cdot sin(\pi-x)\cdot cos(2\pi-x)}=\dfrac{2sin x\cdot cosx\cdot(-tgx)}{(-tgx)\cdot sinx\cdot cos(-x)}=\\\\=\dfrac{2sin x\cdot cosx\cdot(-tgx)}{(-tgx)\cdot sinx\cdot cosx}=2.[/tex]

Green eyes.