cosine law

(redirected from Law of cosines)
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cosine law

1. A physical law that describes the relationship between the sides and angles of any triangle.
2. When applied to physical treatment of the body, it describes the effectiveness of radiant energy and the angle at which it strikes tissue. The maximum amount of energy transfer occurs when the energy strikes tissue at a 90° angle. As the angle changes, the effectiveness of the energy is reduced by the multiple of the cosine of the angle: Effective energy = applied energy × cosine of the angle.
See also: law
Medical Dictionary, © 2009 Farlex and Partners


1. Scattering of light passing through a heterogeneous medium, or being reflected irregularly by a surface, such as a sandblasted opal glass surface. Diffusion by a perfectly diffusing surface occurs in accordance with Lambert's cosine law. In this case, the luminance will be the same, regardless of the viewing direction. 2. The passive movement of ions or molecules through a medium or across a semi-permeable membrane (e.g. the ciliary epithelium) in response to a concentration gradient until equilibrium is reached. It is one of the three mechanisms that create aqueous humour. See diffuse light; diffuse reflection; ultrafiltration.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
The spherical law of cosines is applied to angles formed by the vectors [r.sub.n-1], [r.sub.n], e.
Trigonometrical identities, Pythagorean identities, and laws for obtaining solutions to triangles (i.e., law of sines, law of cosines, and law of tangents) have been derived.
Solving the inverse kinematics for the first and second axis using Pythagoras and Law of cosines
Law of cosines applied to triangle in which K1, K2, K3 represent the three sides of a triangle.
From the law of cosines, we can obtain the following:
The path on the hyperbolic side of the double surface can be described with the hyperbolic law of cosines:
Less frequently seen is the Law of Cosines, which permits calculation of the length of all sides and magnitude of all angles in a triangle, if the length of two sides and magnitude of the angle between them are known.
With clues and in-class preparation, I have found this to be a generally accessible homework problem for students, leading them to their own discovery of the Law of Cosines. Through examples, one can then help students realize that coordinates can be a convenient addition to the context.
This leads to the law of cosines corresponding to the sum of squares basic to the derivation of Gaussian least squares.
While there are many trigonometric formulas, the three most commonly used in EW applications are the Law of Sines, the Law of Cosines for Angles, and the Law of Cosines for Sides.
By the circumference of a circle concluded path s on the elliptic sphere is calculated with the help of the spherical law of cosines.
In a similar manner using the other versions of the law of cosines, we find that [angle]A [congruent to] [angle]D, and that [angle]B [congruent to] [angle]E.

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