2倍根号3sin2x+4sinx+8倍根号3cosx=17

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2倍根号3sin2x+4sinx+8倍根号3cosx=17
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2倍根号3sin2x+4sinx+8倍根号3cosx=17
2倍根号3sin2x+4sinx+8倍根号3cosx=17

2倍根号3sin2x+4sinx+8倍根号3cosx=17
2√3sin2x+4sinx+8√3cosx=17,
设sinx=u,cosx=v,则
u^2+v^2=1,①
4√3uv+4u+8√3v=17,
(4√3v+4)u=17-8√3v,
u=(17-8√3v)/(4√3v+4),②
代入①,去分母得(17-8√3v)^2+(4√3v^2+4v)^2=(4√3v+4)^2,
289-272√3v+192v^2+48v^4+32√3v^3+16v^2=48v^2+32√3v+16,
整理得48v^4+32√3v^3+160v^2-304√3v+273=0,
v1=v2=√3/2,或48v^2+80√3v+364=0(无实根),
代入②,u=1/2,
即sinx=1/2,cosx=√3/2,
∴x=(2k+1/6)π,k∈Z.