# What Is a Cosine?

Cosine is a trigonometric function involving a right angled triangle in mathematics. In this case, a cosine is the sine of a complementary angle where the complementary angle equals the result of subtracting the known angle from a right angle of 90?.
co·sine
[koh-sahyn]
NOUN
1.
Mathematics (of a real or complex number x) the function cos x defined by the infinite series 1 − (x2/2!) + (x4/4!) − + …, where ! denotes factorial. Abbreviation: cos
Source: Dictionary.com
Cosine is the trigonometric function that is the equivalent of the ratio of the side adjacent to an acute angle (only in right-angled triangles) to the hypotenuse. Trigonometric functions are also known as circular functions.
Q&A Related to "What Is a Cosine"
 In various calculus and trigonometry courses, cosine is generally defined as the area of a right triangle in which the ratio of the triangle's length of the side is adjacent to an http://answers.ask.com/Science/Mathematics/what_is...
 In trigonometry, when we look at right triangles, the cosine is the ratio of the length of the adjacent side to the length of the hypotenuse. http://wiki.answers.com/Q/What+is+the+cosine+for+2...
 1. Check the mode of the calculator. On scientific calculators it is displayed on the screen. For graphing calculators, press "Mode. If you are using degrees (generally, if you http://www.ehow.com/how_8113118_cosine-calculator....
 1 Find, using geometry or otherwise, the required variables. There are two cases in which the Cosine Rule can be used: When all three sides of a triangle are known or can be calculated http://www.wikihow.com/Use-the-Cosine-Rule
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In mathematics, especially geometry, a cosine is a ratio of the length an the side adjacent to an acute angle to the length of the hypotenuse. ...
In various calculus and trigonometry courses, cosine is generally defined as the area of a right triangle in which the ratio of the triangle's length of the side ...
According to Mathematics, the Cosine of an angle is the trigonometric function of that angle. When we talk about the value of a cosine, we mean the value of its ...