consequently,

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CD = r - \ / r squared - AD squared . (9)
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[TEX: CD = r - \sqrt{r^2 - \overline{AD^2}}.]

Having obtained C, we put the instrument in the direction A B C. Then
each point of C F describes a circumference of the same center o.

16. If the distance of the points A and B were too great, then it
would be easy to determine a series of points belonging to the arc of
circumference sought (Fig. 4).

Being given C, the direction C I, and C I = R, on C I I lay off C E = d,
draw A E B perpendicularly, and calculate C A or A E. I shall have

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d = (R - d) = AE squared;

[TEX: d = (R - d) = \overline{AE^2};]

or, as absolute value,

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A E = \ / d (R - d) . (10)
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