cos2x+5sinx-3=0
1-2sin²x+5sinx-3=0
-2sin²x+5sinx-2=0
2sin²x-5sinx+2=0
√D=√25-16=√9=3
sinx=1/4[5+3]=2 sinx≤1
sinx=1/4[5-3]=1/2
x=(-1)ⁿπ/6+πk k∈Z
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5sinx+3sin2x=0
5sinx+6sinx*cosx=0
sinx(5+6cosx)=0
5+6cosx=0 cosx=-5/6 x=+-arccos(-5/6)+2πk k∈Z
sinx=0 x=πk k∈Z