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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 hypotenuse2

**:**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}Keep scrolling for more

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Merriam-Webster unabridgedWords at Play

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sineTime Traveler for

sine## The first known use of

sinewas in 1593See more words from the same year