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sin(x+150)=0.5
sin(90+60+x)=0.5
-cos(60+x)=0.5
cos(60+x)=-0.5
60+x=120 degrees...if you are taught general solutions then 60+x=2n(pi)+-(pi)/3
x=60 degrees....if you are taught general solutions then x=2n(pi)+-(pi)/3-(pi)/3
...........................................x=2n(pi)..or...2n(pi)-2(pi)/3