已知cosx=1/3,-派/2

已知cosx=1/3,-派/2
已知cosx=1/3,-派/2

已知cosx=1/3,-派/2
∵cosx=1/3,-π/2∴sinx=-√(1-cosx^2)=-√(1-1/9)=-2√2/3
∴tanx=sinx/cosx=(-2√2/3)/(1/3)=-2√2
∴sin(2π+x)/tan(-x-π)cos(-x)tanx
=-sinx/cosx(tanx)^2
=-(-2√2/3)/[(1/3)*(-2√2)^2]
=√2/4