cosine
nounDefinition of cosine
1 : a trigonometric function that for an acute angle is the ratio between the leg adjacent to the angle when it is considered part of a right triangle and the hypotenuse
2 : a trigonometric function cos θ that for all real numbers θ is given by the sum of the alternating series {latex}1  \frac{x^2}{2!} + \frac{x^4}{4!}  \frac{x^6}{6!} + \frac{x^8}{8!}  \dots{/latex} and that is exactly equal to the cosine of an angle of measure θ in radians
Keep scrolling for more
Keep scrolling for more
Test Your Vocabulary
Words from Greek and Roman Mythology Quiz

 Boreal comes from the name of the ancient Greek god of which wind?
Test your visual vocabulary with our 10question challenge!
TAKE THE QUIZTest Your Knowledge  and learn some interesting things along the way.
TAKE THE QUIZLove words? Need even more definitions?
MerriamWebster unabridgedWords at Play
Ask the Editors
Word Games

Words from Greek and Roman Mythology Quiz
A mythological/etymological mashup!
Take the quiz 
Great Scrabble Words—A Quiz
Words to improve your Scrabble game
Take the quiz 
Name That Thing
Test your visual vocabulary with our 10question challenge!
Take the quiz 
SCRABBLE® Sprint
SCRABBLE® fans, sharpen your skills!
Play the game
Share cosine
Resources for cosine