is an integer
    or the base is positive and f, g are: tan, cot; sin, csc; or cos, sec.

    Examples
    ========

    >>> from sympy.simplify.fu import TR111
    >>> from sympy.abc import x
    >>> from sympy import tan
    >>> TR111(1 - 1/tan(x)**2)
    1 - cot(x)**2

    c