## Elements of Geometry: On the Basis of Dr. Brewster's Legendre : to which is Added a Book on Proportion, with Notes and Illustrations |

### From inside the book

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Page 12

We find that a certain principle is true with respect to a particular diagram ; for example , that the sum of two

We find that a certain principle is true with respect to a particular diagram ; for example , that the sum of two

**adjacent**angles formed by the intersection of two straight lines , is equal to two right - angles . Page 14

When a straight line AB meets another straight line CD , so as to make the

When a straight line AB meets another straight line CD , so as to make the

**adjacent**angles BAC , BAD , equal to each other , each of those angles is called a right - angle ; and the line AB C is said to be perpendicular to CD . Page 17

A diagonal is a line which joins the vertices of two angles not

A diagonal is a line which joins the vertices of two angles not

**adjacent**to each other . Thus the line AC , in the figure above , is a diagonal . 20. An equilateral polygon is one which has all its sides equal ; an equiangular polygon ... Page 20

Every straight line CD , which meets another straight line AB , makes with it two

Every straight line CD , which meets another straight line AB , makes with it two

**adjacent**angles ACD , BCD , the sum of which is equal to two right - angles . At the point C erect CE perpendicuE lar to AB . Page 21

The sum of all the angles BAC , CAD , DAE , EAF , formed on the same side of a straight line BF , is equal to two right - angles ; because their sum is equal to that of the two

The sum of all the angles BAC , CAD , DAE , EAF , formed on the same side of a straight line BF , is equal to two right - angles ; because their sum is equal to that of the two

**adjacent**angles , BAC , CAF . V. B F A PROPOSITION II .### What people are saying - Write a review

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### Common terms and phrases

ABCD Abridgment Academies adjacent altitude antecedent base called centre chord circle circumference circumscribed coincide common cone consequently construction contained convex surface cylinder Day's Algebra demonstration described diagonal diameter difference distant divided draw drawn equal equivalent expressed extremities faces fall figure four frustum geometry given greater half hence hypothesis inscribed interior intersection join lateral less magnitudes manner mean measured meet multiplied number of sides opposite parallel parallelogram parallelopipedon pass perimeter perpendicular plane plane MN polygon principles prism PROBLEM Prop proportional PROPOSITION proved pyramid quantity radii radius ratio reason rectangle regular respectively right-angles Scholium schools segment sides similar solid angle sphere square straight line suppose surface taken tangent THEOREM third triangle triangle ABC vertex whole

### Popular passages

Page 196 - THEOREM. Every section of a sphere, made by a plane, is a circle.

Page 176 - AT into equal parts .Ax, xy, yz, &c., each less than Aa, and let k be one of those parts : through the points of division pass planes parallel to the plane of the bases : the corresponding sections formed by these planes in the two pyramids will be respectively equivalent, namely, DEF to def, GHI to ghi, &c.

Page 125 - AB as a diameter, describe a semicircle : at the extremity of the diameter draw the tangent AD, equal to the side of the square C ; through the point D and the centre O draw the secant DF ; then will DE and DF be the adjacent sides of the rectangle required. For...

Page 229 - The area of the circle, we infer therefore, is equal to 3.1415926. Some doubt may exist perhaps about the last decimal figure, owing to errors proceeding from the parts omitted ; but the calculation has been carried on with an additional figure, that the final result here given might be absolutely correct even to the last decimal place. Since the...

Page 118 - B, may be found in the same manner, for it will be the same as a fourth proportional to the three lines A, B, B. PROBLEM IIL To find a mean proportional between two given lines A and B.

Page 176 - DEF, def, are equivalent; for like reasons, the third exterior prism GHI-K and the second interior prism ghi-d are equivalent; the fourth exterior and the third interior ; and so on, to the last in each series. Hence all the exterior prisms of the pyramid...

Page 46 - 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 220 - Let it be granted that a straight line may be drawn from any one point to any other point.

Page 101 - In every triangle, the square of the side subtending either of the acute angles, is less than the squares of the sides containing that angle, by twice the rectangle contained by either of these sides, and the straight line intercepted between the acute angle and the perpendicular let fall upon it from the opposite angle.

Page 227 - The surface of a regular inscribed polygon, and that of a similar polygon circumscribed, being given ; to find the surfaces of the regular inscribed and circumscribed polygons having double the number of sides. Let AB be a side of the given inscribed polygon ; EF, parallel to AB, a side of the circumscribed polygon ; C the centre of the circle. If the chord AM and the tangents AP, BQ, be drawn, AM...