若cos(α-π)=-2/3求sin(α-2π)+sin(-α-3π)cos(α-3π)÷cos(π-α)-cos(-π-α)cos(α-4π)
若cos(α-π)=-2/3求[sin(α-2π)+sin(-α-3π)cos(α-3π)]÷[cos(π-α)-cos(-π-α)cos(α-4π)]