Photomath в помощь(есть в App Store и play market)
Cos(a-3pi)*sin(3pi/2+a)+2sin(a-pi)*cos(pi/2-a)+sin^2a =
= -cosa*(-cosa) +(-2sina)*(sina)+sin^2a = cos^2a-2sina^2a+sin^2a = cos^2a-sin^2a = cos2a
Б) a^2+1-6a+4
a^2-6a+5
D=36-4*1*5=16
<span>√D=8
x1= 6+8/2=7
x2=6-8/2=-1</span>