5cos^2 x+3sinx cosx=1
5cos^2 x +3sinx cosx -sin^2 x-cos^2 x=0
4cos^2 x +3sinx cosx-sin^2 x=0 |:cos^2 x≠0
4+3tgx-tg^2 x=0
y=tgx; y^2-3y-4=0; D=9-4*(-4)=25=5^2; y1=(3-5)/2=-1; y2=4
tgx=-1 ili tgx=4
x=-π/4+πn x=arctg4+πn; n-celoe
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