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Definition of sine
1 : the trigonometric function that for an acute angle is the ratio between the leg opposite the angle when it is considered part of a right triangle and the hypotenuse
2 : a trigonometric function sin θ that for all real numbers θ is exactly equal to the sine of an angle of measure θ in radians and that is given by the sum of a series of which the first term is θ and succeeding terms alternate in sign with the kth term being a fraction whose numerator consists of θ raised to the exponent 2k  1 and whose denominator is the factorial of 2k  1
Recent Examples of sine from the Web

That onetwo punch, Mr. Achatz later said, was meant to convey a sense of tension and release, a ride from valley to peak along the emotional sine curve.

The link was so clear it could be described in derivative sines and cosines, mathematical concepts taught in college trigonometry.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'sine'. Views expressed in the examples do not represent the opinion of MerriamWebster or its editors. Send us feedback.
Origin and Etymology of sine
Medieval Latin sinus, from Latin, curve
SINE Defined for English Language Learners
sine
playDefinition of sine for English Language Learners

geometry : the ratio between the long side (called the hypotenuse) and the side that is opposite to an acute angle in a right triangle
Learn More about sine

Britannica English: Translation of sine for Arabic speakers Britannica.com: Encyclopedia article about sine
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