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    Re: Radians and Degrees
    From: Paul Hirose
    Date: 2020 Nov 1, 14:05 -0800

    The ′ gauge mark on scale ST coincides with the number of minutes per
    radian (ca. 3440) on scale C. Thus, it helps you convert between minutes
    of arc and radians. And since the measure of a small angle in radians is
    also its sine and tangent at slide rule accuracy, you can get trig
    functions and their inverses.
    For example, Moon horizontal parallax is 59′. What is its distance?
    (Assume Earth radius = 6400 km.)
    1. Set cursor to 59 on D.
    2. Set the ′ mark to cursor.
    3. Set cursor to 6400 km on D.
    4. Read 373 000 km at cursor on C.
    Step 2 puts the C index at sin 59′ on D (about .01715). Step 3
    calculates 6400 km / sin 59′.
    Paul Hirose

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