136 ESSAYS anp OBSERVATIONS 
becaufe as the fine of theangle BCD is to 
the tangent of the angle CDS, fo is the ex- 
cefs of the arc BD above its fine to the arc 
GD; fay, as the radius is to the fine of 
theangle BCD, fo is 57°.2957795, &e. 
the number of degrees in an angle fub- 
tended by an arc equal to the radius, to 
the number of degrees in an angle fub- 
tended by an arc equal to the fine of the 
angle BCD ; (let this angle be called Al. 
Again, as the fine of the angle BCD to 
the tangent of the angle CDS, fo is the ex- 
cefs of the angle BCD above the angle A, 
to the angle GCD. Therefore the angle 
ACG, the anomaly of the excentric, will 
be given. 
Bi SGsIA. MD Pick. 2aeies ae 
In the orbit of Mercury, the mean di- 
ftance is to the excentricity as 109090 to 
20589. Suppofe the mean anomaly from 
the aphelion to be 60°, it is required to 
find the anomaly of the excentric. In the 
triangle BCS, as 120589, the fum of BC, 
CS, is to 79411, the difference of the fides 
BC,CS, fo is the tangent of 32°, half the 
fum 
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