Question

ПОМОГИТЕ ПОЖАЛУЙСТА!!!!!!!!!!!!!!!
1) sin2x2cosx
2) tg^2x(1+cos2x)
3)cos^2-cos2x
4) cos2x-cos^2x1-cos^2x

Answer 1

$frac{Sin2x}{2Cosx} = frac{2SinxCosx}{2Cosx}=Sinx\\tg ^{2}x(1+Cos2x) = frac{Sin ^{2}x }{Cos ^{2}x }*2Cos ^{2} x=2Sin ^{2}x\\Cos ^{2} x-Cos2x=Cos ^{2}x-(Cos ^{2} x-Sin ^{2}x)=Cos ^{2} -Cos ^{2}x+Sin ^{2}x$$=Sin ^{2}x\\ frac{Cos2x-Cos ^{2}x }{1-Cos ^{2}x }= frac{Cos ^{2}x-Sin ^{2}x-Cos ^{2}x }{Sin ^{2} x} = frac{-Sin ^{2}x }{Sin ^{2} x}=-1$