cosine
noun
co·sine ˈkō-ˌsīn 
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
Example Sentences
Recent Examples on the Web The answer: nothing. Remember that the basic trig functions (sine, cosine, tangent) are just ratios of sides of right triangles. 
Rhett Allain, Wired, 14 Mar. 2022 Among the things students are typically taught in high school: how to find the cosine of an angle, what started the War of 1812, and the chemical composition of salt. BostonGlobe.com, 29 Oct. 2021 In 1807, Joseph Fourier discovered that any periodic function — an equation whose values repeat cyclically — could be expressed as the sum of trigonometric functions like sine and cosine. Quanta Magazine, 13 Oct. 2021 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 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 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 The numerical solution above ALSO looks EXACTLY like a cosine function. Rhett Allain, Wired, 2 Nov. 2020 The space agency worked with companies including Intel, Ubotica Technologies, and camera-maker cosine to develop a small cube satellite about the size of a desktop computer called PhiSat-1. Jeremy Kahn, Fortune, 20 Oct. 2020 See More
Rhett Allain, Wired, 14 Mar. 2022 Among the things students are typically taught in high school: how to find the cosine of an angle, what started the War of 1812, and the chemical composition of salt. BostonGlobe.com, 29 Oct. 2021 In 1807, Joseph Fourier discovered that any periodic function — an equation whose values repeat cyclically — could be expressed as the sum of trigonometric functions like sine and cosine. Quanta Magazine, 13 Oct. 2021 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 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 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 The numerical solution above ALSO looks EXACTLY like a cosine function. Rhett Allain, Wired, 2 Nov. 2020 The space agency worked with companies including Intel, Ubotica Technologies, and camera-maker cosine to develop a small cube satellite about the size of a desktop computer called PhiSat-1. Jeremy Kahn, Fortune, 20 Oct. 2020 See More Word History
Etymology
New Latin cosinus, from co- + Medieval Latin sinus sine
First Known Use
1635, in the meaning defined at sense 1