A Rhombus. A Rhombus is a parallelogram, having all its sides equal, its opposite sides parallel, but its angles not right angles. A Rhomboid. A Rhomboid is a parallelogram having its opposite sides equal and parallel, and its angles not right angles. A Trapezoid. D A Trapezoid is a quadrilateral, having only two of its sides parallel. A line drawn through the opposite angles of any plain figure, is a diagonal. The line D G is a diagonal. A Trapezium. A Trapezium is a quadrilateral, having none of its sides parallel. What are Quadrilateral figures? What are Parallelograms? Draw and explain the properties of a Square; an Oblong; a Rhombus ; a Rhomboid; a Trapezoid ; a Trapezium; a Diagonal line. Which of these figures are parallelograms, and which are not? SECTION IV. Multilateral Figures, or Polygons. Figures having many sides, are called Multilaterals. They are also called Polygons, because they have many angles. Polygons which have equal sides and equal angles, are called regular polygons. Those which have not are called irregular polygons. A Pentagon has five sides and five angles. A Heptagon has seven sides and seven angles. The number of sides and angles in a Polygon might be multiplied to infinity. It would then become a Circle. What are Multilateral figures? Why are they called Polygons? What are are Regular Polygons? Irregular Polygons? What is a polygon with eight sides and eight angles called? What is one with ten sides and ten angles called? What is a figure with four equal sides and four equal angles called? three sides and three angles called? with an infinite number of sides and A Circle. B What is a figure with What is a polygon angles called? A D A Circle is a regular polygon with an infinite number of sides and angles, all equally distant from the centre. The curve line A B C D bounding the figure is called the periphery, or circumference. the Circle. The space enclosed is A straight line drawn through the centre of a circle and dividing it into two equal parts, is the Diameter. The line D M is a Diameter. A line drawn from the centre to the circumference a circle is a Radius; two or more are Radii. A line drawn through any part of a circle less than a diameter, is called a Chord. The line A C is a Chord. Any part of the circumference is an Arc of a Circle. The curve line AR C is an Arc. A line drawn from the extremity of an arc perpendicular to the radius or diameter is the Sine of an arc. The part of the radius or diameter uniting with the other extremity of the arc is the Versed Sine. The line SE is the Sine of the arc V E. The line V S is the Versed Sine of the arc V E. |