## Observational Geometry |

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### Common terms and phrases

ABCD aid of compasses Calculate the area centre chord circumference compasses and ungraduated cone corners cube cubic centimetres curved surface cylinder Decagon decimetres diagonals diagram will need diameter diedral angles distance divided draw a line Draw two straight drawn edges 5 cm equilateral triangle feet frustum Geometry given straight line graduated ruler greatest number hexagon horizontal Icosagon inscribed lateral surface length measure metres middle points millimetres multiplied need paper Nonagon number of edges number of lines number of points obtuse one-half parallel lines Parallel Ruler parallelogram parallelopiped Pentagon perpendicular plane plumb line points of division points of intersection prism problem protractor pyramid quadrilateral radii radius equal rectangle regular polygon rhombus right angle right triangle secant sector shape sides slant height solid angle special figure sphere square with edges symmetrical tangent three angles three straight lines total number trapezoid ungraduated ruler vertex vertices volume

### Popular passages

Page 183 - The area of a parallelogram is equal to the product of its base and its height: A = bx h.

Page 108 - The radius of a sphere is a straight line, drawn from the centre to any point of the surface ; the diameter, or axis, is a line passing through this centre, and terminated on both sides by the surface.

Page 52 - The formula states that the square of the hypotenuse of a right triangle is equal to the sum of the squares of the base and altitude.

Page 219 - The areas of two similar triangles (or polygons) are to each other as the squares of any two corresponding sides.

Page 87 - 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 184 - The area of a triangle is equal to one-half the product of its base and altitude.

Page 113 - The area of the surface of a sphere is four times the area of a great circle.

Page 164 - AB of the circle into as many equal parts as the polygon is to have sides. With the points A and B as centers and radius AB, describe arcs cutting each other at C.

Page 49 - To draw a straight line through a given point parallel to a given straight line. Let A be the given point, and BC the given straight line ; it is required to draw a straight line through the point A, parallel to the straight hue BC.

Page 186 - Hence the area of a trapezoid is equal to its altitude, multiplied by the line which joins the middle points of the sides which are not parallel.