## Elements of Geometry and Trigonometry: From the Works of A.M. Legendre |

### From inside the book

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**DIAGONAL**of a polygon is a straight line joining the vertices of two angles , not consecutive . 24. A BASE of a polygon is any one of its sides on which the polygon is supposed to stand . 25. Triangles may be classified with reference ... Page 45

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**diagonals**AC , AD . The polygon will be divided into as many triangles , less two , as it has sides , having the point A for a common vertex , and for bases , the sides of the polygon , except the two which form the E angle A. It is ... Page 47

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**diagonal**BD . Then , because AB and DC are parallel , the angle DBA is equal to its alternate D A B angle BDC ( P. XX . , C. 2 ) : and , because AD and BC are parallel , the angle BDA is equal to its alternate angle DBC . The triangles ... Page 48

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**diagonal**DB . triangles ADB and CBD , will have D C the sides of the one equal to the sides of the other , each to each ; and therefore , the triangles will be equal in all of their parts : hence , the angle ABD is equal to the angle ... Page 49

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**diagonals**of a parallelogram divide each other into equal parts , or mutually bisect each other . A C Let ABCD be a parallelogram , and B AC , BD , its**diagonals**: then will AE be equal to EC , and BE to ED . For , the triangles BEC and ...### Other editions - View all

### Common terms and phrases

ABē ABCD ACē adjacent angles altitude apothem Applying logarithms base and altitude bisect centre chord circle circumference circumscribed coincide cone consequently convex surface corresponding cosec cosine Cotang cylinder denote diagonals diameter difference distance divided draw drawn edges equally distant feet find the area Formula frustum given angle given straight line greater hence homologous hypothenuse included angle interior angles intersection less Let ABC log sin lower base mantissa measured by half number of sides opposite parallel parallelogram parallelopipedon perimeter perpendicular plane MN polyedral angle polyedron prism PROPOSITION proved pyramid quadrant radii radius rectangle regular polygons right angles right-angled triangle Scholium secant segment semi-circumference side BC similar sine slant height sphere spherical polygon spherical triangle square subtracted Tang tangent THEOREM triangle ABC triangular prisms triedral angle upper base vertex vertices whence

### Popular passages

Page 126 - The square of the hypothenuse is equal to the sum of the squares of the other two sides ; as, 5033 402+302.

Page 59 - A'B'C', and applying the law of cosines, we have cos a' = cos b' cos c' + sin b' sin c' cos A'. Remembering the relations a' = 180° -A, b' = 180° - B, etc. (this expression becomes cos A = — cos B cos C + sin B sin C cos a.

Page 18 - The circumference of every circle is supposed to be divided into 360 equal parts called degrees, and each degree into 60 equal parts called minutes, and each minute into 60 equal parts called seconds, and these into thirds, fourths, &c.

Page 104 - The square described on the hypothenuse of a rightangled triangle is equal to the sum of the squares described on the other two sides.

Page 6 - The logarithm of any power of a number is equal to the logarithm of the number multiplied by the exponent of the power.

Page 28 - If two triangles have two sides of the one equal to two sides of the...

Page 46 - All the interior angles of any rectilineal figure, together with four right angles, are equal to twice as many right angles as the figure has sides.

Page 99 - The area of a parallelogram is equal to the product of its base and altitude.

Page 172 - If two planes are perpendicular to 'each other, a straight line drawn in one of them, perpendicular to their intersection, will be perpendicular to the other.

Page 214 - A sphere is a solid bounded by a curved surface, every point of which is equally distant from a point within called the center.