**Angle** is also used to designate the measure of an angle or of a rotation. This measure is the ratio of the length of a circular arc to its radius. In the case of an angle (figure), the arc is centered at the vertex and delimited by the sides. In the case of a rotation, the arc is centered at the center of the rotation and delimited by any other point and its image by the rotation.

The word *angle* comes from the Latin word *angulus*, meaning "a corner". The word *angulus* is a diminutive, of which the primitive form, *angus*, does not occur in Latin. Cognate words are the Greek ἀγκύλος *(ankylοs)*, meaning "crooked, curved," and the English word "ankle". Both are connected with the Proto-Indo-European root **ank-*, meaning "to bend" or "bow".

Euclid defines a plane angle as the inclination to each other, in a plane, of two lines which meet each other, and do not lie straight with respect to each other. According to Proclus an angle must be either a quality or a quantity, or a relationship. The first concept was used by Eudemus, who regarded an angle as a deviation from a straight line; the second by Carpus of Antioch, who regarded it as the interval or space between the intersecting lines; Euclid adopted the third concept, although his definitions of right, acute, and obtuse angles are certainly quantitative.

Read more about Angle: Measuring Angles, Identifying Angles, Types of Angles, Angles Between Curves, Dot Product and Generalisation, Inner Product, Angles Between Subspaces, Angles in Riemannian Geometry, Angles in Geography and Astronomy

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... reflects inside the prism twice, allowing the transmission of an image through a right

**angle**without inverting it (that is, without changing the image's ... by total internal reflection, since the beams are incident at an

**angle**less than the critical

**angle**(the minimum

**angle**for total internal reflection) ... of the prism is not used optically but truncates what would otherwise be an awkward

**angle**joining the two mirrored faces ...

... and thinnest it is concave, and extends from the medial

**angle**to the base of the coracoid process ... cavity, and inclines obliquely downward and backward to the inferior

**angle**... the longest of the three, and extends from the medial to the inferior

**angle**...

**Angle**s in Geography and Astronomy

... and longitude of any location in terms of

**angles**subtended at the centre of the Earth, using the equator and (usually) the Greenwich meridian as references ... The

**angle**between those lines can be measured, and is the angular separation between the two stars ... One could say, "The Moon's diameter subtends an

**angle**of half a degree." The small-

**angle**formula can be used to convert such an angular measurement into a distance/si ...

**Angle**

... These two

**angles**combine to define sunrise to occur when the Sun's center is 50 arcminutes below the horizon, or 90.83° from the zenith ...

**Angle**s

... There are 3

**angles**The superior

**angle**is covered by trapezius ... The inferior

**angle**is covered by latissimus dorsi ... The lateral or glenoid

**angle**is broad and bears the glenoid cavity or fossa, which is directed forward, laterally and slightly upwards ...

### Famous quotes containing the word angle:

“The inhabitants of earth behold commonly but the dark and shadowy under side of heaven’s pavement; it is only when seen at a favorable *angle* in the horizon, morning or evening, that some faint streaks of the rich lining of the clouds are revealed.”

—Henry David Thoreau (1817–1862)

“I fly in dreams, I know it is my privilege, I do not recall a single situation in dreams when I was unable to fly. To execute every sort of curve and *angle* with a light impulse, a flying mathematics—that is so distinct a happiness that it has permanently suffused my basic sense of happiness.”

—Friedrich Nietzsche (1844–1900)

“It is a mistake, to think the same thing affects both sight and touch. If the same *angle* or square, which is the object of touch, be also the object of vision, what should hinder the blind man, at first sight, from knowing it?”

—George Berkeley (1685–1753)