若a是锐角,且sin(x-π/6)=1/3,则cosx等于?
问题描述：
若a是锐角,且sin(x-π/6)=1/3,则cosx等于?
答
sin(x-π/6)=sinx*cosπ/6-cosx*sinπ/6=1/3,因为cosx=根号1-sin^2x,化简前式得,4cos^2x+4/3cosx-23/9=0解得cosx=(2根号6-1)/6
若a是锐角,且sin(x-π/6)=1/3,则cosx等于?
sin(x-π/6)=sinx*cosπ/6-cosx*sinπ/6=1/3,因为cosx=根号1-sin^2x,化简前式得,4cos^2x+4/3cosx-23/9=0解得cosx=(2根号6-1)/6