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REZOLVATI
(cos 2x – 2cosx – 3)/(cox -2) – (cos 2x+ cosx – 3)/ (cox +2) = ?


Răspuns :

(cos 2x – 2cosx – 3)/(cox -2) – (cos 2x+ cosx – 3)/ (cox +2) =
(2 cos²x – 1 – 2cos x -3)/ (cosx -2) – (2cos²x – 1 + 2cosx – 3)/(cosx + 2) =
(2cos²x – 2cosx – 4)/(cosx-2) – (2cos²x + 2cosx – 4)/(cosx-2) =
2[ (cos²x – cosx – 2)/(cosx-2) – (cos²x + cosx – 2 )/ (cosx +2)]=
(a) - (b)

a = (cos x- 2)(cosx + 1)/ ( cox -2)
b = (cosx+2) (cosx - 1)/ cos(x+2)
facem simplificarile si  avem
= 2(cosx + 1 – cosx + 1)
  = 4