m sympy import cos, sin
    >>> from sympy.abc import x
    >>> TR11(sin(x/3)/(cos(x/6)))
    sin(x/3)/cos(x/6)
    >>> _TR11(sin(x/3)/(cos(x/6)))
    2*sin(x/6)
    >>> TR11(sin(x/6)/(sin(x/3)))
    sin(x/6)/sin(x/3)
    >>> _TR11(sin(x/6)/(sin(x/3)))
    1/(2*cos(x/6))

    c