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The 90-degree complement to the angle of incidence is called the grazing angle or glancing angle. Incidence at small grazing angles is called "grazing incidence." [citation needed] Grazing incidence diffraction is used in X-ray spectroscopy and atom optics, where significant reflection can be achieved only at small values of the grazing angle.
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. Most protractors measure angles in degrees (°). Radian ...
In trigonometry, the gradian – also known as the gon (from Ancient Greek γωνία (gōnía) 'angle'), grad, or grade [1] – is a unit of measurement of an angle, defined as one-hundredth of the right angle; in other words, 100 gradians is equal to 90 degrees.
Angle trisection is the construction, using only a straightedge and a compass, of an angle that is one-third of a given arbitrary angle. This is impossible in the general case. For example, the angle 2 π /5 radians (72° = 360°/5) can be trisected, but the angle of π /3 radians (60°) cannot be trisected. [8]
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".
A degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of a plane angle in which one full rotation is 360 degrees. [4] It is not an SI unit—the SI unit of angular measure is the radian—but it is mentioned in the SI brochure as an accepted unit. [5]
Speed square, or rafter square, or rafter angle square, or triangle square, or layout square A speed square is a triangular carpenters square combining functions of the combination square, try square, and framing square into one. It can be used to calculate and mark angles, to suspend a plumb bob, and as a fence for a circular saw. [21] [22] [23]
For example, for 35 mm film which is 36 mm wide and 24 mm high, = would be used to obtain the horizontal angle of view and = for the vertical angle. Because this is a trigonometric function, the angle of view does not vary quite linearly with the reciprocal of the focal length.