\ ˈsīn How to pronounce sine (audio) \

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 the alternating series {latex}\sin \theta = \theta - \frac{\theta^{3}}{3!} + \frac{\theta^{5}}{5!} - \frac{\theta^{7}}{7!} + \frac{\theta^{9}}{9!} - \dots{/latex}

Examples of sine in a Sentence

Recent Examples on the Web Markets move through something of a sine, cosine pattern from a seller’s market to a buyer’s market and back again. David Friedman, Forbes, 24 May 2021 The Suns will make the playoffs for the first time sine 2010. Dan Gelston, Star Tribune, 22 Apr. 2021 The Suns will make the playoffs for the first time sine 2010. Dan Gelston, ajc, 22 Apr. 2021 As an example, consider an operator that transforms a function into its derivative (turning the sine of x into the cosine of x, for example, or x3 into 3x2, and so on). Quanta Magazine, 19 Apr. 2021 Usual kingpin Duke missed the field for the first time sine 1995. Scott Gleeson, USA TODAY, 29 Mar. 2021 It was well known by then that the goat problem could be reduced to a single transcendental equation, which by definition includes trigonometric terms like sine and cosine. Quanta Magazine, 9 Dec. 2020 Since the sine of 90 is 1, this gives you the maximum torque for that force and torque-arm. Rhett Allain, Wired, 7 Dec. 2020 The steering still feels disconnected at times—during an initial dive-in toward the apex, or running straight over low-frequency-sine-wave pavement at high speeds—but this is the last impractical-to-remove foible in a 19-year-old chassis. Don Sherman, Car and Driver, 31 Aug. 2020

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 Merriam-Webster or its editors. Send us feedback.

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First Known Use of sine

1593, in the meaning defined at sense 1

History and Etymology for sine

Medieval Latin sinus, from Latin, curve

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Cite this Entry

“Sine.” Dictionary, Merriam-Webster, Accessed 28 Jul. 2021.

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English Language Learners Definition of sine

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

More from Merriam-Webster on sine

Britannica English: Translation of sine for Arabic Speakers Encyclopedia article about sine


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