## An Introduction to the Theory and Practice of Plane and Spherical Trigonometry, and the Stereographic Projection of the Sphere: Including the Theory of Navigation ... |

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Page 82

**Subtract the sum of the two depressions from the contained arc , and half the remainder is the mean refraction**. ( Z ) If one of the objects ( a ) instead of being depressed ...### What people are saying - Write a review

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### Other editions - View all

An Introduction to the Theory and Practice of Plain and Spherical ... Thomas Keith No preview available - 2017 |

An Introduction to the Theory and Practice of Plain and Spherical ... Thomas Keith No preview available - 2014 |

### Common terms and phrases

acute altitude Answer apparent applied base called centre chords circle co-tangent compasses complement consequently CONSTRUCTION contained cosec cosine declination describe difference distance divided division double draw drawn elevation equal equation EXAMPLE extent extremes fall feet figure find the angle formed fourth given gives greater half hand height Hence horizon hypothenuse latitude less logarithm longitude manner mean measured meridian middle miles natural North object oblique observed obtuse opposite parallel perpendicular Plate pole PRACTICAL primitive produced projected proportion PROPOSITION quadrant radius remainder represent Required right angles right-angled spherical triangle RULE scale secant side side ac similar SOLUTION species sphere straight line subtract sun's supplement Suppose tang tangent term third true vers versed sine yards

### Popular passages

Page 25 - The circumference of every circle is supposed to be divided into 360 equal parts, called degrees ; each degree into 60 equal parts, called minutes ; and each minute into 60 equal parts, called seconds.

Page 138 - Consequently, a line drawn from the vertex of an isosceles triangle to the middle of the base, bisects the vertical angle, and is perpendicular to the base.

Page 6 - And if the given number be a proper vulgar fraction ; subtract the logarithm of the denominator from the logarithm of the numerator, and the remainder will be the logarithm sought ; which, being that of a decimal fraction, must always have a negative index.

Page xxvi - A New Treatise on the Use of the Globes; or, a Philosophical View of the Earth and Heavens : comprehending an Account of the Figure, Magnitude, and Motion of the Earth : with the Natural Changes of its Surface, caused by Floods, Earthquakes, Ac.

Page 32 - The CO-SINE of an arc is the sine of the complement of that arc as L.

Page 31 - The sine, or right sine, of an arc, is the line drawn from one extremity of the arc, perpendicular to the diameter passing through the other extremity. Thus, BF is the sine of the arc AB, or of the arc BDE.

Page 242 - The HORIZON is a great circle which separates the visible half of the heavens from the invisible ; the earth being considered as a point in the centre of the sphere of the fixed stars.

Page 242 - ... ZENITH DISTANCE of any celestial object is the arc of a vertical circle, contained between the centre of that object and the zenith ; or it is what the altitude of the object wants of 90 degrees.

Page 199 - The sum of the two sides of a triangle is to their difference as the tangent of half the sum of the angles at the base is to the tangent of half their difference.

Page 32 - The SECANT of an arc, is a straight line drawn from the center, through one end of the arc, and extended to the tangent which is drawn from the other end.