8sina-9cosa/6cos-7sina, если tga=2

Question

8sina-9cosa/6cos-7sina, если tga=2

Answer 1

Cos²a=1: (1+tg²a)=1:(1+4)=1/5
cosa=1/√5
sina=√1-1/5=√4/5=2/√5
(8sina-9cosa)/(6cosa-7sina)=(16/√5 -9/√5)/(6/√5 - 14/√5)=7/√5 :(-8/√5)=
=7/√5 *(-√5/8)=-7/8