Elements of Geometry and Trigonometry Translated from the French of A.M. Legendre by David Brewster: Revised and Adapted to the Course of Mathematical Instruction in the United States |
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Page 10
... four sides , a quadrilateral ; that of five , a pentagon ; that of six , a hexagon ; that of seven , a heptagon : that of eight , an octagon ; that of nine , a nonagon ; that of ten , a decagon ; and that of twelve , a dodecagon . C 15 ...
... four sides , a quadrilateral ; that of five , a pentagon ; that of six , a hexagon ; that of seven , a heptagon : that of eight , an octagon ; that of nine , a nonagon ; that of ten , a decagon ; and that of twelve , a dodecagon . C 15 ...
Page 16
... four angles formed about a point by two straight lines , which intersect each other , are together equal to four right angles : for the sum of the two angles ACE , ECB , is equal to two right angles ; and the sum of the other two , ACD ...
... four angles formed about a point by two straight lines , which intersect each other , are together equal to four right angles : for the sum of the two angles ACE , ECB , is equal to two right angles ; and the sum of the other two , ACD ...
Page 27
... four acute angles are equal to each other , and so also are the four obtuse angles . PROPOSITION XXI . THEOREM . If a straight line meet two other straight lines , making the sum of the interior angles on the same side less than two ...
... four acute angles are equal to each other , and so also are the four obtuse angles . PROPOSITION XXI . THEOREM . If a straight line meet two other straight lines , making the sum of the interior angles on the same side less than two ...
Page 30
... as there are units in the number of sides diminished by two . Cor . 1. The sum of the angles in a quadrilateral is equal to two right angles multiplied by 4-2 , which amounts to four right angles : hence , if all the angles of 30 GEOMETRY .
... as there are units in the number of sides diminished by two . Cor . 1. The sum of the angles in a quadrilateral is equal to two right angles multiplied by 4-2 , which amounts to four right angles : hence , if all the angles of 30 GEOMETRY .
Page 31
... four right angles . Let the sides of the polygon ABCD- FG , be produced , in the same direction ; then will the sum of the exterior angles a + b + c + d + f + g , be equal to four right angles . A a F D B / b For , each interior angle ...
... four right angles . Let the sides of the polygon ABCD- FG , be produced , in the same direction ; then will the sum of the exterior angles a + b + c + d + f + g , be equal to four right angles . A a F D B / b For , each interior angle ...
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Common terms and phrases
adjacent altitude angle ACB angle BAC ar.-comp base multiplied bisect Book VII centre chord circ circumference circumscribed common cone consequently convex surface cosine Cotang cylinder diagonal diameter dicular distance divided draw drawn equal angles equally distant equations equivalent feet figure find the area formed four right angles frustum given angle given line gles greater homologous sides hypothenuse inscribed circle inscribed polygon intersection less Let ABC logarithm measured by half number of sides opposite parallelogram parallelopipedon pendicular perimeter perpen perpendicular plane MN polyedron polygon ABCDE PROBLEM proportional PROPOSITION pyramid quadrant quadrilateral quantities radii radius ratio rectangle regular polygon right angled triangle Scholium secant segment side BC similar sine slant height solid angle solid described sphere spherical polygon spherical triangle square described straight line tang tangent THEOREM triangle ABC triangular prism vertex
Popular passages
Page 241 - In every plane triangle, the sum of two sides is to their difference as the tangent of half the sum of the angles opposite those sides is to the tangent of half their difference.
Page 251 - Being on a horizontal plane, and wanting to ascertain the height of a tower, standing on the top of an inaccessible hill, there were measured, the angle of elevation of the top of the hill 40°, and of the top of the tower 51° ; then measuring in a direct line 180 feet farther from the hill, the angle of elevation of the top of the tower was 33° 45' ; required the height of the tower.
Page 109 - The perimeters of two regular polygons of the same number of sides, are to each other as their homologous sides, and their surfaces are to each other as the squares of those sides (Book IV.
Page 91 - Two similar triangles are to each other as the squares described on their homologous sides. Let ABC, DEF, be two similar triangles, having the angle A equal to D, and The angle B=E.
Page 169 - THEOREM. 7?/6 convex surface of a cylinder is equal to the circumference of its base multiplied by its altitude.
Page 41 - CIRCLE is a plane figure bounded by a curved line, all the points of which are equally distant from a point within called the centre; as the figure ADB E.
Page 155 - AK. The two solids AG, AQ, having the same base AEHD are to each other as their altitudes AB, AO ; in like manner, the two solids AQ, AK, having the same base AOLE, are to each other as their altitudes AD, AM. Hence we have the two proportions, sol.
Page 86 - The areas of two triangles which have an angle of the one equal to an angle of the other are to each other as the products of the sides including the equal angles. A D A' Hyp. In triangles ABC and A'B'C', To prove AABC A A'B'C' A'B' x A'C ' Proof. Draw the altitudes BD and B'D'.
Page 282 - ... 1. To find the length of an arc of 30 degrees, the diameter being 18 feet. ' Ans. 4.712364. 2. To find the length of an arc of 12° 10', or 12£°, the diameter being 20 feet.
Page 93 - ABC : FGH : : ACD : FHI. By the same mode of reasoning, we should find ACD : FHI : : ADE : FIK; and so on, if there were more triangles. And from this series of equal ratios, we conclude that the sum of the antecedents...