The term cosine is a mathematical concept used in trigonometry. It is defined as the RATIO of the length of the side adjacent to an angle in a right triangle to the length of the hypotenuse. The crossword solutions for cosine include 'RATIO' (5 letters), 'ratios' (6 letters), 'ARC' (3 letters), 'SECANT' (6 letters), 'secants' (7 letters), and 'sineand' (7 letters). Ratios refer to the relationship between two or more numbers, arcs are curved lines, secants are lines that intersect a circle at two points, and sineand is a combination of the words sine and cosine.