已知cos(a+π/3)=1/3 a是锐角 求cosa
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已知cos(a+π/3)=1/3a是锐角求cosa已知cos(a+π/3)=1/3a是锐角求cosa已知cos(a+π/3)=1/3a是锐角求cosacosa=cos[(a+π/3)-π/3]=cos
已知cos(a+π/3)=1/3 a是锐角 求cosa
已知cos(a+π/3)=1/3 a是锐角 求cosa
已知cos(a+π/3)=1/3 a是锐角 求cosa
cosa
=cos[(a+π/3)-π/3]
=cos(a+π/3)cosπ/3+sin(a+π/3)sinπ/3
=(1/3)*(1/2)+(2√2/3)*(√3/2)
=(1+2√6)/6.