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1.2.2.PYRAMIDS
Apyramid(Figure1.18)isapolyhedronwhoseonefaceisn-sidedpolygoncalled
abaseofapyramid,andotherfacesaretriangleswithonecommonvertexcalled
apex.
Figure1.18.Elementsofpyramid
Thenameofapyramiddependsuponitsbasepolygon.Forexample,apyra-
midwithanoctagonasabaseiscalledoctagonalpyramid.Whenalllateraledges
areequalinlength,apyramidiscalledright.Whenabaseisaregularpolygonand
alllateralfacesarecongruentisoscelestriangles,apyramidiscalledregular.The
altitudefootofaregularpyramidisacentreofacircumcircleofthebase.
Forsimplicitytriangularpyramidiscalledtetragon.Examplesofpyramidsare
giveninFigure1.19.
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Figure1.19.Examplesofpyramids