1. 

   Jacviah New Member

   Вычислитьtg9°-tg63°+tg81°-tg27°

    

   Jacviah, 16 янв 2010

   #1
2. 

   Alex0777 New Member

   tg9-tg63+tg81-tg27 = 
   = tg9+tg81-(tg27+tg63) =
   = tg9+tg(90-9) - (tg27+tg(90-27)) =
   = tg9+Ctg9 - (tg27+Ctg) =
   = 1/(cos9*sin9)-1/(cos27*sin27) =
   = 2/sin18 - 2/sin54 =
   = 2*(sin54-sin18)/(sin18*cos36) =
   = 2*2*sin18*cos36/(sin18*cos36) = 4 

    

   Alex0777, 16 янв 2010

   #2

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