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In geometry and trigonometry, a right angle is an angle of exactly 90 degrees or / 2 radians [1] corresponding to a quarter turn. [2] If a ray is placed so that its endpoint is on a line and the adjacent angles are equal, then they are right angles. [ 3 ]
One could say, "The Moon's diameter subtends an angle of half a degree." The small-angle formula can convert such an angular measurement into a distance/size ratio. Other astronomical approximations include: 0.5° is the approximate diameter of the Sun and of the Moon as viewed from Earth. 1° is the approximate width of the little finger at ...
The foreshortening factor (1/2 in this example) is inversely proportional to the tangent of the angle (63.43° in this example) between the projection plane (colored brown) and the projection lines (dotted). Front view of the same. Oblique projection is a type of parallel projection: it projects an image by intersecting parallel rays (projectors)
A square is a tool used for marking and referencing a 90° angle, though mitre squares are used for 45° angles. Squares see common use in woodworking, metalworking, construction and technical drawing. [1] Some squares incorporate a scale for measuring distances (a ruler) or for calculating angles.
A prism diagonal uses a simple 90°-angle prism, pentaprism, or an Amici roof prism rather than a mirror to bend the optical path. On telescopes with a longer focal ratios, a well-made 90° prism diagonal is the optimum choice to deliver the highest image contrast short of using the telescope without a diagonal entirely.
With a flat image plane, 90° is the widest field of view that can be captured in focus and without significant wide-angle distortion or vignetting. Lenses with an imaging angle approaching 120 degrees require a center filter to correct vignetting at the edges of the image.
A right triangle ABC with its right angle at C, hypotenuse c, and legs a and b,. A right triangle or right-angled triangle, sometimes called an orthogonal triangle or rectangular triangle, is a triangle in which two sides are perpendicular, forming a right angle (1 ⁄ 4 turn or 90 degrees).
So a standard 50 mm lens for 35 mm photography acts like a 50 mm standard "film" lens on a professional digital SLR, but would act closer to an 80 mm lens (1.6×50mm) on many mid-market DSLRs, and the 40-degree angle of view of a standard 50 mm lens on a film camera is equivalent to an 80 mm lens on many digital SLRs.