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A half-circle protractor marked in degrees (180°). A protractor is a measuring instrument, typically made of transparent plastic, for measuring angles. Some protractors are simple half-discs or full circles. More advanced protractors, such as the bevel protractor, have one or two swinging arms, which can be used to help measure the angle.
[18] [19] Today, the degree, 1 / 360 of a turn, or the mathematically more convenient radian, 1 / 2 π of a turn (used in the SI system of units) is generally used instead. In the 1970s – 1990s, most scientific calculators offered the gon (gradian), as well as radians and degrees, for their trigonometric functions . [ 23 ]
For example, the degree is defined such that one turn is 360 degrees. Using metric prefixes, the turn can be divided in 100 centiturns or 1000 milliturns, with each milliturn corresponding to an angle of 0.36°, which can also be written as 21′ 36″. [16] [17] A protractor divided in centiturns is normally called a "percentage protractor".
In physics, there are equations in every field to relate physical quantities to each other and perform calculations. Entire handbooks of equations can only summarize most of the full subject, else are highly specialized within a certain field. Physics is derived of formulae only.
For example, an angle of 30 degrees is already a reference angle, and an angle of 150 degrees also has a reference angle of 30 degrees (180° − 150°). Angles of 210° and 510° correspond to a reference angle of 30 degrees as well (210° mod 180° = 30°, 510° mod 180° = 150° whose supplementary angle is 30°).
This includes mostly instruments which measure macroscopic properties of matter: In the fields of solid-state physics; in condensed matter physics which considers solids, liquids, and in-betweens exhibiting for example viscoelastic behavior; and furthermore, in fluid mechanics, where liquids, gases, plasmas, and in-betweens like supercritical ...
Finally, the initial angle could be measured with a simple protractor. It is difficult to position and read the initial angle with high accuracy (or precision, for that matter; this measurement has poor reproducibility). Assume that the students consistently mis-position the protractor so that the angle reading is too small by, say, 5 degrees ...
The length is copied from the point to O'. This will become the centre used by circular protractor. Draw a line from here to crossing of the vertical and the long-line. The circular protractor is aligned so that zero falls on the new line. Points are marked off and lines drawn through them to the long line.