O angle is the measure of the gap between two straight segments. Thus, there is a number that is related to each opening between two rays, and the larger the opening, the greater this number.
formal definition
Angle is a measure expressed in degrees that is attributable to the region or set of points located between two ray lines of the same origin.
Usually the angles are represented by capital letters with a circumflex accent, by lowercase letters or, in the case of the figure above, as follows: BÂC.
measuring angles
The measures assigned to the angles function differently from those used to measure distances. The angles are based on the circle. When increasing an angle, one of the rays will move, as if it were on a circle where their meeting point is the center. Therefore, it is not possible to use a ruler to obtain angle measurements.
The equipment used to take measurements of angles It is known as protractor and is illustrated in the figure below:
To use it, place one of the straight lines on the first line of the
protractor, the one that points to zero. Afterwards, place the meeting point of the semi-straights in the center of the equipment, which is usually marked on it. After that, the angle to be measured will be the number where the second ray points.
the remarkable angles
Some angles are more observed by man in nature. It was they who gave rise to the specific choice of numbers used to measure angles. The angle known as shallow, for example, which is defined when one ray is kept fixed and the other describes a half-turn movement, has been assigned a value of 180°.
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Angle formed by half-turn: 180° angle
An interesting property of the shallow angle is that the ray that forms it, when connected, can be seen as a single straight line, that is, given a point on a straight line, the angle formed at that point is 180°.
It is believed that these values were chosen at a time when men believed that the year had 360 days. Each day was considered as a unit of measurement of the angle described by the Earth around the sun and, therefore, an entire revolution would be 360°.
Another important angle is known as straight angle and its measurement is equal to 90°. This angle is often found in civil construction, in the “corners” formed by two walls. Its importance is so great that there is a tool created exclusively to help build this type of "corner" and to measure this angle: o square.
the others remarkable angles are studied in trigonometry and their measurements are: 30°, 45° and 60°.
Remarkable angles studied in trigonometry
By Luiz Paulo Moreira
Graduated in Mathematics
Would you like to reference this text in a school or academic work? Look:
SILVA, Luiz Paulo Moreira. "What is an angle?"; Brazil School. Available in: https://brasilescola.uol.com.br/o-que-e/matematica/o-que-e-angulo.htm. Accessed on June 28, 2021.
