## A Treatise on Special Or Elementary Geometry: In Four Parts. Including Plane, Solid, and Spherical Geometry, and Plane and Spherical Trigonometry, with the Necessary Tables, Part 3 |

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### Common terms and phrases

ABCD allel altitude angle included anharmonic ratio base bisect bisector centre of similitude chord circumference circumscribed circumscribed circle common point constant construct DEM.-Let diagonals diameter diedral distance divided draw a line equal angles equations equilateral triangles figure fixed point geometrical given circle given line given point harmonic conjugate harmonic mean harmonic pencil harmonic proportion Hence homologous hypotenuse inscribed circle intersection isoperimetric isosceles triangle line drawn line joining line parallel line passing medial line middle point opposite sides pendicular perpendicular polar pole polyedron polygon Prob.-Find the locus proposition quadrilateral radical axis radii radius rectangle regular regular polygon right angled triangle right line secant solid angles square straight line student SUG's symmetrical with respect tangent tetraedron Theo.-If Theo.-The third side transversal vertex whence

### Popular passages

Page 292 - Find the locus of a point such that the sum of the squares of its distances from two fixed points shall be equivalent to the square of the distance between the fixed points.

Page 292 - Find the locus of a point the sum of whose distances from two fixed intersecting lines is constant, ie, is equal to a given line.

Page 250 - The square described on the hypothenuse of a right-angled triangle is equivalent to the sum of the squares described on the other two sides.

Page 245 - If from any point there extend two lines tangent to a circumference, the angle contained by the tangents is double the angle contained by the line joining the points of contact and the radius extending to one of them.

Page 270 - To describe a circle with a given radius, which shall pass through a given point and be tangent to a given line.

Page 249 - From this proposition it is evident, that the square described on the difference of two lines is equivalent to the sum of the squares described on the lines respectively, minus twice the rectangle contained by the lines.

Page 310 - Three lines are in harmonical proportion, when the first is to the third, as the difference between the first and second, is to the difference between the second and third ; and the second is called a harmonic mean between the first and third. The expression 'harmonical proportion...

Page 294 - O'O" as at O. With 0 as a centre and OA as a radius, describe a circle. Then is this circumference the locus required. For, let BC be any secant line passing through A, we may show that P is the middle point of BC- [Having done this, as above, and shown that any point not in this circumference is not the middle of the secant line passing through A, his solution is complete.] SYS.

Page 267 - The intersection of two spherical surfaces is the circumference of a circle whose plane is perpendicular to the line joining the centres of the surfaces and whose centre is in that line. Let 0, 0' be the centres of the spherical surfaces, and let a plane passing through 0, 0' cut the spheres in great circles whose circumferences intersect in the points A and B.

Page 275 - A' parallel to A, FIG. 427. and the figure will suggest the construction. 803. To pass a plane through a given line and tangent to a given sphere. SUo's.—Pass a plane through the centre of the sphere and perpendicular to the given line. Through the point of intersection and in this secant plane draw tangents to the great circle in which the secant plane intersects the surface of the sphere. The points of tangency will be the points of tangency of the required planes (?), of which there are thus...