protractor

protractor
/proh trak"teuhr, preuh-/, n.
1. a person or thing that protracts.
2. (in surveying, mathematics, etc.) an instrument having a graduated arc for plotting or measuring angles.
3. Anat. a muscle that causes a part to protrude.
[1605-15; < ML; see PROTRACT, -TOR]

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Instrument for constructing and measuring plane angles.

The simplest protractor is a semicircular disk marked in degrees from 0° to 180°. A more complex protractor, for plotting position on navigation charts, is called a three-arm protractor, or station pointer, and consists of a circular scale connected to three arms. The centre arm is fixed, while the outer two can be rotated to any desired angle relative to the centre one. A related instrument is the course protractor, which allows navigators to measure the angular distance between north and the course plotted on a navigation chart.

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▪ measurement instrument
any of a group of instruments used to construct and measure plane angles. The simplest protractor comprises a semicircular disk graduated in degrees—from 0° to 180°. It is an ancient device that was already in use during the 13th century. At that time, European instrument makers constructed an astronomical observing device called the torquetum that was equipped with a semicircular protractor.

A more complex form of protractor, designed for plotting the position of a ship on navigational charts, was invented in 1801 by Joseph Huddart, a U.S. naval captain. This instrument, called a three-arm protractor, or station pointer, is composed of a circular scale connected to three arms. The centre arm is fixed, while the outer two are rotatable, capable of being set at any angle relative to the centre one.

A related instrument used by marine navigators is the course protractor. It provides an effective tool with which to measure the angular distance between magnetic north and the course plotted on a navigational chart.

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Universalium. 2010.

Look at other dictionaries:

• Protractor — Pro*tract or, n. 1. One who, or that which, protracts, or causes protraction. [1913 Webster] 2. A mathematical instrument for laying down and measuring angles on paper, used in drawing or in plotting. It is of various forms, semicircular,… …   The Collaborative International Dictionary of English

• protractor — PROTRACTÓR, OÁRE adj., s. m. (muşchi) care are rolul de a întinde un membru sau o parte a corpului spre înainte. (< fr. protracteur) Trimis de raduborza, 15.09.2007. Sursa: MDN …   Dicționar Român

• protractor — 1610s, one who lengthens (an action), agent noun from L. protrahere (see PROTRACT (Cf. protract)); sense of instrument for drawing angles first recorded 1650s …   Etymology dictionary

• protractor — the instrument used in geometry, is spelt or, not er …   Modern English usage

• protractor — ► NOUN ▪ an instrument for measuring angles, typically in the form of a flat semicircle marked with degrees along the curved edge …   English terms dictionary

• protractor — [prō′trak΄tər, prō trak′tər] n. [ML] 1. a person or thing that protracts 2. an instrument in the form of a graduated semicircle, used for plotting and measuring angles 3. Anat. a muscle that protracts, or extends, a limb …   English World dictionary

• Protractor — In geometry, a protractor is a circular or semicircular tool for measuring an angle or a circle. The units of measurement utilized are usually degrees.Some protractors are simple half discs; these have existed since ancient times. More advanced… …   Wikipedia

• protractor —    A semicircular tool for the measurement and construction of angles. On the flat side of the protractor in the middle is either a hole or cross hairs. This is where the vertex (point of the angle) must go when measuring. Usually a horizontal… …   Glossary of Art Terms

• protractor — matlankis statusas T sritis Standartizacija ir metrologija apibrėžtis Įtaisas kampams matuoti ir žymėti brėžinyje. atitikmenys: angl. angle protractor; protractor; semicircular protractor vok. Winkelmesser, n rus. транспортир, m pranc. demi… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

• protractor — matlankis statusas T sritis fizika atitikmenys: angl. angle protractor; protractor; semicircular protractor vok. Transporteur, m; Winkelmesser, n rus. транспортир, m pranc. demi cercle gradué, m; rapporteur, m …   Fizikos terminų žodynas