The Collaborative International Dictionary
Sinical
Sinical \Sin"i*cal\, a. [From Sine.] (Trig.) Of or pertaining to a sine; employing, or founded upon, sines; as, a sinical quadrant.
Douglas Harper's Etymology Dictionary
sinical
"of or relating to sines," 1590s, from sine + -ical.
Wiktionary
sinical
a. (context dated mathematics English) of, relating to, or constructed using sines