# cosine law

(redirected from Law of cosines)
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## cosine law

[kō′sīn]
a rule that optimal irradiation occurs when the source of radiation is at right angles to the center of the area being irradiated.

## 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.

## diffusion

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.
References in periodicals archive ?
Law of cosines applied to triangle in which K1, K2, K3 represent the three sides of a triangle.
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.
Referring again to Figure 1, if the length of sides A and B and the angle c between them are known, the Law of Cosines allows the length of side C to be calculated:
Using Figure 2, we show below that, knowing the displacement d of the center of the drilled hole of diameter r from the center of the circular pad of radius R, one can calculate the breakout angle 2t by using the Law of Cosines.
10 and 11 allow calculation of breakout angle by utilizing the Law of Cosines.
This generalization of the Pythagorean Formula is called The Law of Cosines.
In particular, we may ask how The Law of Cosines can be expressed for the triangle located in the plane by the three points [P.
Writing the terms of the Law of Cosines using the coordinate representations just obtained, and canceling like terms, we get that [x.
The spherical law of cosines (5) with the help of the simplified Hardy approximation (14) enables to calculate the approximate value of the sphere radius in cases of a tiny curvature where Pythagoras' theorem approximately rules.
By the circumference of a circle concluded path s on the hyperbolic sphere is calculated with the help of the hyperbolic law of cosines.
A common calculator supports the spherical law of cosines only for radius up to ~ [10.
Now, using the law of cosines in triangle ABC we have that

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