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    Re: Need formulas for arcsin and arctan
    From: Lu Abel
    Date: 2006 Mar 28, 09:30 -0800

    Whoops, in first paragraph should have said "You get radians by
    MULTIPLYING the angle in degrees by 2*Pi/360.
    > We are most familiar with measuring angles in degrees.  Mathematicians
    > like to measure them in radians which is a more "natural" unit (for
    > example, the formulae for calculating sines and cosines require an angle
    > to be measured in radians).  There are 2*Pi radians going all the way
    > around a circle, just as there are 360 degrees.  You get radians by
    > dividing the angle in degrees by 2*Pi/360.  Your scientific calculator
    > will offer the option of expressing angles in either radians or degrees.
    > On the other hand, regardless of whether an angle is expressed as 45
    > degrees or Pi/4 radians, its sine and cosine are the same.   So scanning
    > down a table that expresses angles in degrees for a sine or cosine that
    > matches your calculation should give you arcsine(x) in degrees.
    > Lu Abel
    > Bill wrote:
    >>> Finally, since arcsine(x) is simply "the angle whose sine is x" scanning
    >>> down a conventional table of sines will easily give you the answer to a
    >>> degree...
    >> Exposing my ignorance (again), arcsine is a bit confusing to me.  Every
    >> definition I find in my (old) reference books relates it to an angle in
    >> radians.
    >> As an analogy, "font" had a specific meeting prior to the computer.  It
    >> meant not only a font "family" bit a specific size, weight, slant,
    >> compressions or expansion, designer or foundry etc..  12 pt Caslon No.
    >> 540
    >> Italic was one font, 14 pt Caslon No. 540 Italic another font, as was 36
    >> point Bodoni Campanile (Ludlow).  Now "font" is a very loose description,
    >> tied mostly to the intellectual-property laws.
    >> So my question, is/was "arcsine" a term that applied only to "the angle
    >> whose sine is x," in radians, while sin^-1 can apply to whatever system
    >> (degrees, rads, grads) one is working in?
    >> Thanks
    >> Bill

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