The Collaborative International Dictionary of English v.0.48:

Trigonometric \Trig`o*no*met"ric\, Trigonometrical
\Trig`o*no*met"ric*al\, [Cf. F. trigonom['e]trique.]
   Of or pertaining to trigonometry; performed by the rules of
   trigonometry.
   [1913 Webster] --Trig`o*no*met"ric*al*ly, adv.
   [1913 Webster]

   Trigonometrical curve, a curve one of whose coordinates is
      a trigonometric function of the other.

   Trigonometrical function. See under Function.

   Trigonometrical lines, lines which are employed in solving
      the different cases of plane and spherical trigonometry,
      as sines, tangents, secants, and the like. These lines, or
      the lengths of them, are trigonometrical functions of the
      arcs and angles to which they belong.

   Trigonometrical survey. See under Survey.
      [1913 Webster]

WordNet (r) 3.0 (2006):

trigonometric
    adj 1: of or relating to or according to the principles of
           trigonometry; "trigonometric function"