2cos x*sin x - sin^2 x - 2sin x - 2cos x + sin x + 2 = cos^2 x
2cos x*sin x - sin x - 2cos x + 2 = cos^2 x + sin^2 x = 1
2cos x*sin x - 2cos x - sin x + 1 = 0
2cos x*(sin x - 1) - (sin x - 1) = 0
(2cos x - 1)(sin x - 1) = 0
1) cos x = 1/2; x1 = +- pi/3 + 2pi*k
2) sin x = 1; x2 = pi/2 + 2pi*k
X-9+x=90
2x-9=90
2x=99
x=49,5
________
49,5-9+49,5=90
Ответ:х=49,5
№1
1) (х+у)(х-13) = х*х-х*13+ух*13 = х²-13х+ху-13у
2) (m+18)*(y+3) = my+3m+18y+18*3 = my+3m+18y+54
2) (m+12)*(y-3) = my-m*3-12y-12*3 = my-3m+12y-36
№2
(3m²+5mn+7m²y)-(5mn+3m²)-(7m³y-3m²) = 3m²+5mn+7m²y-5mn-3m²-7m³y+3m² = 7m²y-7m³y+3m²