def chebmul(c1, c2):
<EOL>[c1, c2] = pu.as_series([c1, c2])<EOL>z1 = _cseries_to_zseries(c1)<EOL>z2 = _cseries_to_zseries(c2)<EOL>prd = _zseries_mul(z1, z2)<EOL>ret = _zseries_to_cseries(prd)<EOL>return pu.trimseq(ret)<EOL>
Multiply one Chebyshev series by another.

Returns the product of two Chebyshev series `c1` * `c2`.  The arguments
are sequences of coefficients, from lowest order "term" to highest,
e.g., [1,2,3] represents the series ``T_0 + 2*T_1 + 3*T_2``.

Parameters
----------
c1, c2 : array_like
    1-D arrays of Chebyshev series coefficients ordered from low to
    high.

Returns
-------
out : ndarray
    Of Chebyshev series coefficients representing their product.

See Also
--------
chebadd, chebsub, chebdiv, chebpow

Notes
-----
In general, the (polynomial) product of two C-series results in terms
that are not in the Chebyshev polynomial basis set.  Thus, to express
the product as a C-series, it is typically necessary to "reproject"
the product onto said basis set, which typically produces
"unintuitive live" (but correct) results; see Examples section below.

Examples
--------
>>> from numpy.polynomial import chebyshev as C
>>> c1 = (1,2,3)
>>> c2 = (3,2,1)
>>> C.chebmul(c1,c2) # multiplication requires "reprojection"
array([  6.5,  12. ,  12. ,   4. ,   1.5])