In mathematics, cosine means: In a right triangle, the ratio of the side next to an angle (the adjacent side) to the hypotenuse; it is written cos, so cos 60° = 0.5.
In Turkish: kosinüs
How it is used
The 'CAH' in SOH CAH TOA: cosine = adjacent over hypotenuse. The cosine rule, c² = a² + b² − 2ab cos C, works in any triangle. 'cos x' is read 'coz x' or 'cosine x'.
Example sentences
Use the cosine rule to find the third side of the triangle.
The cosine of 90 degrees is zero.
Common collocations
cosine rule
cosine of an angle
inverse cosine
cosine graph
Related terms
sineIn a right triangle, the ratio of the side opposite an angle to the hypotenuse; it is written sin, so sin 30° = 0.5.
tangentIn a right triangle, the ratio of the opposite side to the adjacent side, written tan; also a straight line that touches a curve at a point without cutting across it there.
hypotenuseThe longest side of a right triangle, which is the side opposite the right angle.
radianA unit for measuring angles: the angle at the centre of a circle made by an arc as long as the radius. A full turn is 2π radians, or 360°.
Practise with graded reading
Reading at the right level is the fastest way to make new words stick. Pick free English books by level:
