""""""""""""""""""""""""""""""""""""""
- x^2 = - 2x + 2
x^2 - 2x + 2 = 0
D = 4 - 4*2 = 4 - 8 <0
нет реш
Д=в2-4ас=25-4х9х9=25+244=
1-sinacosa/tga=1-sinacosa/(sina/cosa)=
=1-sinacosa(cosa/sina)=1-cos²a=sin²a
tga≠0,a≠kπ,k∈Z
(tga=sina/cosa, sin²a+cos²a=1)