Sin²x-sinx=0
sinx(sinx-1)=0
sinx=0 и sinx=1
x=πn,n€Z.... x=π/2+2πn,n€Z
2)10cos²x+3cosx-1=0
Пусть cosx=t(|t|≤1)
10t²+3t-1=0
D=9+40=49; √D=7
t1=(-3-7)/20=-1/2
t2=(-3+7)/20=1/5
Замена:
cosx=-1/2
x=±2π/3+2πn, n € Z
cosx=1/5
x=±arccos1/5+2πn, n € Z
3)5sin²x+cosx-5=0
5-5cos²x+cosx-5=0
5cos²x-cosx=0
cosx(5cosx-1)=0
cosx=0
x=π/2+πn, n € Z
cosx=1/5
x=±arccos1/5+2πn, n € Z