Click on the image to see just the image,

IN MATH: 1. n, an angle measure (symbol rad may be used, though no symbol is needed).
EX. A right angle (90°) measures radians, 1.57079632679489... radians.
EX. Simplify .

IN MATH: 2. n. 1 radian is a constant, like pi, and e, and the square root of 2.  It is about 57.3, but is irrational like the other constants listed here. It divides the circle into nice, simple, pieces. Angle measures need not be written in degrees, but may be written as numbers.

See:   Radians & Sectors Using radianSector.gsp: video, Sketchpad, worksheet, answers
key words: angle, circle formulas from middle school, special angles, degree measures, radians, radian measures, arc, arc length, sector, angular speed
See:   Angle Measure, a history of angle measurement, web page,   video,   page pdf file
key words -- ancient counting and communication of numbers, Egyptian mathematics, Sumerian/Babylonian mathematics, construction of a hexagon, Roman/Greek mathematics, pi, radians, graph papers, other tools sfor teaching radians
    Turn a fraction to a decimal as in: 1/2= .5, 1/4 = .25
    Multiply by as in: 2 = 6.283..., /2 = 1.571

    To convert degrees to radians, multiply the number of degrees by 180 then divide by .     This calculator will do that for you.

    Input degrees, press equal, get radian written in decimal form.

Enter negatives as "-x" rather than "- x"
degrees radians.

    To convert radians to degrees, multiply the number of radians by and divide by 180.     This calculator will do that for you.

    Input radians (as a decimal), press equal, get degree measure written in decimal form.

Enter negatives as "-x" rather than "- x"
radians degrees.

5.1 Circle's arcs and sectors

    Radians make circle computation and these formulas MUCH easier and clearer.

    For the full story, see Arc Formulas and Rational, and Sector Formulas and Rational.

    Click on the image below to see an enlargement of the formulas that are used here.

    Input the data.
  1. radius =
  2. central angle measure in degrees =
  3. time (if needed) =
    Press button to obtain the computed measure.
  1. arc length, s, units of length
  2. linear speed (unit of length)/(unit of time)
  3. angular speed degrees/(unit of time)
  4. area of sector square units

IN ENGLISH: 1. as defined above.

APPLICATION: See list 330.


This is a page from the dictionary MATH SPOKEN HERE!, published in 1995 by MATHEMATICAL CONCEPTS, inc., ISBN: 0-9623593-5-1.

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