law of sines

American  

noun

Trigonometry.

1. a law stating that the ratio of a side of a plane triangle to the sine of the opposite angle is the same for all three sides.

2. a law stating that the ratio of the sine of an arc of a spherical triangle to the sine of the opposite angle is the same for all three arcs.

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Example Sentences

In their talk at the American Mathematical Society meeting, Jackson and Johnson said a trigonometric identity called the law of sines didn’t depend on the Pythagorean theorem and that they could use it to prove the theorem.

From Scientific American

Such are that the rays of light are propagated in straight lines; that the angles of reflexion and of incidence are equal; and that in refraction the ray is bent according to the law of sines, now so well known, and which is no less certain than the preceding laws.

From Project Gutenberg