2cos^2x+14cosx=3sinx^2x

Question

2cos^2x+14cosx=3sinx^2x

Answer 1

2cos^2x+14cosx-3+3cos^2x=0

5cos^2x+14cosx-3=0

cosx=t

5t^2+14t-3=0

D=196+60=256

t=-14+16/10=1/5

t=-30/10 не подхоодит

cosx=1/5

x= + - arccos1/5+2nk