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The sine and cosine of an acute angle are defined in the context of a right triangle: for the specified angle, its sine is the ratio of the length of the side that is opposite that angle to the length of the longest side of the triangle (the hypotenuse ), and the cosine is the ratio of the length of the adjacent leg to that of the hypotenuse.
The Greek letter θ (theta) is used as a variable in mathematics to represent an angle. The symbol appears in the three main trigonometric functions: cosine, sine, and tangent as an input argument.
Sine, Cosine and Tangent (often shortened to sin, cos and tan) are each a ratio of sides of a right angled triangle: For a given angle θ each ratio stays the same. no matter how big or small the triangle is. To calculate them: Divide the length of one side by another side. Example: What is the sine of 35°?
Notation. Conventionally, an abbreviation of each trigonometric function's name is used as its symbol in formulas. Today, the most common versions of these abbreviations are "sin" for sine, "cos" for cosine, "tan" or "tg" for tangent, "sec" for secant, "csc" or "cosec" for cosecant, and "cot" or "ctg" for cotangent.
Definitive list of the most common symbols in geometry and trigonometry, categorized by function into tables along with each symbol's meaning and example. Learn Hub
Cosine is a periodic function. A periodic function is a function, f, in which some positive value, p, exists such that. f (x+p) = f (x) for all x in the domain of f, p is the smallest positive number for which f is periodic, and is referred to as the period of f.
The Law of Cosines. For any triangle ... a, b and c are sides. C is the angle opposite side c. ... the Law of Cosines (also called the Cosine Rule) says: c 2 = a 2 + b 2 − 2ab cos (C) It helps us solve some triangles. Let's see how to use it. Example: How long is side "c" ... ? We know angle C = 37º, and sides a = 8 and b = 11.
