4sin^2x-7sinxcosx+3cos^2x=1

Cos3x+2cos2x+cosx=0

4sin²x-7sinxcosx+3cos²x-sin²x-cos²x=0

3sin²x-7sinxcosx+2cos²x=0 / cos²x

3tg²x-7tgx+2=0

tgx=t

3t²-7t+2=0

D=49-24=25

t1=7-5/6=2/6=1/3

t2=7+5/6=12/6=2

tgx=1/3 tgx=2

x=arctg1/3+pi*n x=arctg2+pi*n

2) 2cos2xcosx+2cos2x=0

2cos2x (cosx+1) = 0

cos2x=0 cosx+1=0

2x=pi/2+pi*n cosx=-1

x=pi/4+pi*n/2 x=pi+2pi*n