## An Elementary Treatise on Plane and Spherical Trigonometry: With Their Applications to Navigation, Surveying, Heights and Distances, and Spherical Astronomy, and Particularly Adapted to Explaining the Construction of Bowditch's Navigator and the Nautical Almanac |

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ABC fig adjacent ascension and declination azimuth calculated celestial celestial equator celestial sphere circle column computed Corollary corr corresponding cosec cosine cotan course denote departure diff difference of latitude difference of longitude dist earth earth's centre ecliptic equal to 90 equator find the sine formula given angle gives Greenwich Hence horizon horizontal parallax hour angle hypothenuse included angle interval logarithm mean meridian altitude method middle latitude miles moon moon's motion Nautical Almanac Navigator obliquity obtuse parallax Parallel Sailing perpendicular plane plane of reference pole position Problem Prop proportion radius rhumb right ascension Scholium secant second member semidiameter sideral solar Solution solve the triangle spherical right triangle spherical triangle star star's sun's tang tangent transit Trig trigonometric functions Trigonometry vernal equinox vertical whence zenith

### Popular passages

Page 44 - In any plane triangle, the sum of any two sides is to their difference as the tangent of half the sum of the opposite angles is to the tangent of half their difference.

Page 125 - II. The sine of the middle part is equal to the product of the cosines of the opposite parts.

Page 109 - PROBLEM III. To find the height of an INACCESSIBLE OBJECT above a HORIZONTAL PLANE. 11. TAKE TWO STATIONS IN A VERTICAL PLANE PASSING THROUGH THE TOP OF THE OBJECT, MEASURE THE DISTANCE FROM ONE STATION TO THE OTHER, AND THE ANGLE OF ELEVATION AT EACH. If the base AB (Fig.

Page 41 - To find a side, work the following proportion: — as the sine of the angle opposite the given side is to the sine of the angle opposite the required side, so is the given side to the required side.

Page 245 - Solar Day is the interval of time between two successive transits of the sun over the same meridian ; and the hour angle of the sun is called Solar Time. This is the most natural and direct measure of time. But the intervals between the successive returns of the sun to the meridian are not exactly equal, but depend upon the variable> motion of the sun in right ascension. - The want of uniformity in the sun's motion in right ascension arises from two different causes ; one, that the sun does not move...

Page 117 - A spherical triangle is a portion of the surface of a sphere, bounded by three arcs of great circles.

Page 125 - NAPIER'S CIRCULAR PARTS. Thus, in the spherical triangle A. BC, right-angled at C, the circular parts are p, b, and the complements of h, A, and B. 167. When any one of the five parts is taken for the middle part, the two adjacent to it, one on either side, are called the adjacent parts, and the other two parts are called the opposite parts. Then, whatever be the middle part, we have as THE EULES OF NAPIER.

Page 163 - The cosine of half the sum of two sides of a spherical triangle is to the cosine of half their difference as the cotangent of half the included angle is to the tangent of half the sum of the other two angles. The sine of half the sum of two sides of a spherical...

Page 99 - Now the sum of the areas of the triangles is the area of the polygon, and the sum of the angles of the triangles is the sum of the angles of the polygon.

Page 301 - Twilight begins and ends when the sun is about 18° below the horizon.