The Practice of Navigation: And Nautical Astronomy

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J. D. Potter, 1882 - Nautical astronomy - 910 pages
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Page 41 - The angle in a semicircle is a right angle ; the angle in a segment greater than a semicircle is less than a right angle; and the angle in a segment less than a semicircle is greater than a right angle.
Page 19 - The characteristic of a number less than 1 is found by subtracting from 9 the number of ciphers between the decimal point and the first significant digit, and writing — 10 after the result.
Page 38 - A parallelogram is a four.sided figure, of which the opposite sides are parallel; and the diameter is the straight line joining two of its opposite angles.
Page vii - This is the more important, as very indistinct and erroneous notions prevail among practical persons on the subject of accuracy of computation ; and much time is, in consequence, often lost in computing to a degree of precision wholly inconsistent with that of the elements themselves. The mere habit of working invariably to a useless precision, while it can never advance the computer's knowledge of the subject, has the unfavourable tendency of deceiving those who are not aware of the true nature...
Page 147 - For the same body the semidiameter varies with the distance; thus, the difference of the sun's semidiameter at different times of the year is due to the change of the earth's distance from the sun; and similarly for the moon and the planets.
Page 22 - A CIRCLE is a figure bounded by a curve line called the circumference,* of which every point is at the same distance from a point within, called the centre. Thus, ABD is a circle, and C the centre.
Page 43 - ... section shall be parallel to the remaining side of the triangle. Let DE be drawn parallel to BC, one of the sides of the triangle ABC: then BD shall be to DA, as CE to EA. Join BE, CD; then the triangle BDE is equal...
Page 37 - ... the three interior angles of' a triangle are together equal to two right angles.
Page 39 - Hence it is plain that triangles on the same or equal bases, and between the same parallels, are equal, seeing (by cor.
Page 105 - The distance between two points on the surface of a sphere is the length of the minor arc of a great circle between them.

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