5-2sin2x-6cos^2x=0

да 5t²-4t-1=0

D=16+20=36;t=(4±6)/10

t1=1;t2=-1/5

tgx=1;x=π/4+πk

tgx=-1/5;x=arctg(-1/5)+πk

5-2sin2x-6cos²x=05sin²x+5cos²x-4sinxcosx-6cos²x=05sin²x-cos²x-4sinxcosx=0 (:cos²x#0)5tg²x-4tgx-1=0tgx=t5t²-4t-1=0D=16+20=36=6²t=(4±6)/10t1=1;t2=-1/51)tgx=1x=π/4+πk;k€Z2)tgx=-1/5x=-arctg(1/5)+πk;k€Z