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P ' is the inverse of P with respect to the circle. To invert a number in arithmetic usually means to take its reciprocal. A closely related idea in geometry is that of "inverting" a point. In the plane, the inverse of a point P with respect to a reference circle (Ø) with center O and radius r is a point P ', lying on the ray from O through P ...
Since C = 2πr, the circumference of a unit circle is 2π. In mathematics, a unit circle is a circle of unit radius—that is, a radius of 1. [1] Frequently, especially in trigonometry, the unit circle is the circle of radius 1 centered at the origin (0, 0) in the Cartesian coordinate system in the Euclidean plane.
The meaning of these terms is apparent if one looks at the functions in the original context for their definition, a unit circle: For a vertical chord AB of the unit circle, the sine of the angle θ (representing half of the subtended angle Δ) is the distance AC (half of the chord).
So the inverse of a circle is the same circle if and only if it intersects the unit circle at right angles. To summarize and generalize this and the previous section: The inverse of a line or a circle is a line or a circle. If the original curve is a line then the inverse curve will pass through the center of inversion.
The complex numbers of absolute value one form the unit circle. Adding a fixed complex number to all complex numbers defines a translation in the complex plane, and multiplying by a fixed complex number is a similarity centered at the origin (dilating by the absolute value, and rotating by the argument).
Or, "the arc whose cosine is x" is the same as "the angle whose cosine is x", because the length of the arc of the circle in radii is the same as the measurement of the angle in radians. [5] In computer programming languages, the inverse trigonometric functions are often called by the abbreviated forms asin, acos, atan. [6]
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Circle inversion through the unit circle is a transformation of the plane that, in polar coordinates, maps the point (,) (excluding the origin) to (,) and vice versa. [23] The image of an Archimedean spiral r = φ a {\displaystyle r={\tfrac {\varphi }{a}}} under this transformation (its inverse curve ) is the hyperbolic spiral with equation r ...