Sine and cosine - Wikipedia The word cosine derives from an abbreviation of the Latin complementi sinus 'sine of the complementary angle ' as cosinus in Edmund Gunter 's Canon triangulorum (1620), which also includes a similar definition of cotangens
Cosines - Clark University Cosines Definition of cosine The cosine of an angle is defined as the sine of the complementary angle The complementary angle equals the given angle subtracted from a right angle, 90° For instance, if the angle is 30°, then its complement is 60° Generally, for any angle θ, cos θ = sin (90° – θ) Written in terms of radian measurement, this identity becomes cos θ = sin (π 2
Cosine Made Easy (Trigonometry) - Andrea Minini The Latin term " cosinus " was coined by the English mathematician and astronomer Edmund Gunter in the 17th century The term cosine was introduced much later than the term sine