Re: [sympy] Solve does not handle trigonometric equations

[Chris Smith]

In the current master [1] you get

```

>>> solve(sin(x)+tan(x))

[0, 2*pi]

>>> solve(sin(x)+sec(x))

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

  File "sympy\solvers\solvers.py", line 834, in solve

    solution = _solve(f[0], *symbols, **flags)

  File "sympy\solvers\solvers.py", line 1339, in _solve

    result = _tsolve(f_num, symbol, **flags)

  File "sympy\solvers\solvers.py", line 2166, in _tsolve

    return _solve(rewrite - rhs, sym)

  File "sympy\solvers\solvers.py", line 1345, in _solve

    "\nNo algorithms are implemented to solve equation %s" % f)

NotImplementedError: multiple generators [exp(I*x), sec(x)]

No algorithms are implemented to solve equation sec(x)

```

But give that a little help by rewriting it and it works:

```

>>> solve((sin(x)+sec(x)).rewrite(cos)

... )

[-2*atan(-1/2 + sqrt(2 - 2*sqrt(3)*I)/2 + sqrt(3)*I/2), 2*atan(1/2 - sqrt(3)*I/2

 + sqrt(2 - 2*sqrt(3)*I)/2), 2*atan(1/2 - sqrt(2 + 2*sqrt(3)*I)/2 + sqrt(3)*I/2)

, 2*atan(1/2 + sqrt(2 + 2*sqrt(3)*I)/2 + sqrt(3)*I/2)]

```

[Chris Smith]

[1] http://tinyurl.com/7oqpu7v  (how to get the most recent SymPy)

[Abhishek kumawat]

I installed the latest using git and tried your example using rewrite:

<ipython-input-7-6d87796777b3> in <module>()

----> 1 solve(sin(x)+sec(x)).rewrite(cos)

C:\Python27\lib\site-packages\sympy\core\expr.pyc in __float__(self)

    239         if result.is_number and result.as_real_imag()[1]:

    240             raise TypeError("can't convert complex to float")

--> 241         raise TypeError("can't convert expression to float")

    242

    243     def __complex__(self):

TypeError: can't convert expression to float

[Chris Smith]

Did you check to see that you didn't set x to something? This will be fixed, btw, with PR 1964 so you don't have to do the rewrite manually.

[Chris Smith]

You are missing a left paren after "solve" and then a closing one:

solve(sin(x)+sec(x)).rewrite(cos) -->

solve((sin(x)+sec(x)).rewrite(cos))

[Chris Smith]

Note that this will "just work" in PR 1964.