Take the 2-minute tour ×  So, I have an arc that's part of a
circle that I must "travel across".  The circle has a radius of
$15$ - a circumference of $94.248$ (rounding). The arc length in
question is equal to $15.708$.  Now, normally, you could sort of
walk along the arc, turning with it. But, if I could only travel
straight, I need to know how I would get from one part of the
arc to $15.708$ units later in the arc of the circle (only being
able to travel straight, or make $90$ degree turns).
share|improve this question Very related. –  Ｊ. Ｍ. Dec 6 '11 at
18:48 add comment  2 Answers  For a thousand years, the only
extensive trigonometric table was about precisely this question:
see Ptolemy's table of chords.  If the central angle is $\theta$
and the diameter is $d$, then the length of the chord is
$d\sin(\theta/2)$.  Observe that $\dfrac{15.708}{94.248}=\dfrac
16$, so the central angle is $60^\circ$. For a $60^\circ$ angle,
the length of the chord is exactly the radius.  share|improve
this answer add comm