giai giup em bai tap voi

C

connguoivietnam

a/ 2(tanx/2-1)=cosx
2[sin(x/2)/cos(x/2)-1]=cosx
2[sin(x/2)+cos(x/2)]/cos(x/2)=cosx
2[sin(x/2)+cos(x/2)]/cos(x/2)=cos^2(x/2)-sin^2(x/2)
2[sin(x/2)+cos(x/2)]/cos(x/2)=[cos(x/2)-sin(x/2)].[cos(x/2)+sin(x/2)]
[sin(x/2)+cos(x/2)].[2/cos(x/2)-cos(x/2)+sin(x/2)]=0
sin(x/2)+cos(x/2)=0
2/cos(x/2)-cos(x/2)+sin(x/2)=0
 
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