在 數學 中， 正弦 （英語：sine、縮寫 ）是一種 週期函數，是 三角函数 的一種。 它的 定义域 是整个 实数集， 值域 是 。 它是 周期函数，其最小正周期为 （ ）。 在自变量为 （ ，其中 为 整数）时，该函数有极大值1；在自变量为 （ ）时，该函数有 极小值 -1。 正弦函数是 奇函数，其图像于 原点 对称。 在半个最小正周期内，正弦函数有反函数，称为 反正弦函数。 正弦的符号为 ，取自拉丁文sinus，词源是梵文的jiva（“弓弦”，如今多写作jya）。 这个词在阿拉伯语里转写 …

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 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.

正弦（sine），数学术语，是三角函数的一种，在直角三角形中，任意一锐角∠A的对边与斜边的比，叫作∠A的正弦，记作sinA（由英语sine一词简写得来），即sinA=∠A的对边/斜边。

\sec x = \frac{1}{\cos{x}} \csc{x} = \frac{1}{\sin{x}} \cot{x} = \frac{1}{\tan{x}} 平方关系 \sin^{2}x + \cos^{2}x = 1. 1 + \tan^{2} x = \sec^{2}x. 1 + \cot^{2}x = \csc^{2}x. 商关系 \tan{x} = \frac{\sin{x}}{\cos{x}} = \frac{\sec{x}}{\csc{x}} \cot{x} = \frac{\cos{x}}{\sin{x}} = \frac{\csc{x}}{\sec{x}} 三角恒等变换公式 和差公式

Sine Function: sin (θ) = Opposite / Hypotenuse. Cosine Function: cos (θ) = Adjacent / Hypotenuse. Tangent Function: tan (θ) = Opposite / Adjacent. When we divide Sine by Cosine we get: So we can say: That is our first Trigonometric Identity. We can also divide "the other way around" (such as Adjacent/Opposite instead of Opposite/Adjacent) to get:

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2025年2月18日 · In a right triangle, the sine of an angle θ is defined as: sin⁡ (θ) = opposite side / hypotenuse. Opposite side: The side opposite to the given angle. Hypotenuse: The longest side of the right triangle, opposite the right angle. Adjacent side: The side that touches both the given angle and the right angle.

Sine, Cosine and Tangent (often shortened to sin, cos and tan) are each a ratio of sides of a right angled triangle: To calculate them: Divide the length of one side by another side. Example: What is the sine of 35°? Using this triangle (lengths are only to one decimal place): = …

The sine function is one of the basic functions encountered in trigonometry (the others being the cosecant, cosine, cotangent, secant, and tangent). Let be an angle measured counterclockwise from the x -axis along an arc of the unit circle. Then is the vertical coordinate of the arc endpoint, as illustrated in the left figure above.

Sine function is one of the three primary functions in trigonometry, the others being cosine, and tan functions. The sine x or sine theta can be defined as the ratio of the opposite side of a right triangle to its hypotenuse.