The   kind   of   geometry   that   we   will   be   using   in   this   manual   is   called plane   geometry.   Plane   geometry   deals   with   points,   lines,   polygons   (A shape   with   more   than   two   sides,   i.e.   square,   triangle,   hexagon,   etc.) and   circles   on   a   flat   surface   (plane).   Sheet   metal   flat   patterns   are done in plane geometry. Solid   geometry   deals   with   points,   lines,   and   planes   in   space,   (3 dimensional).   When   our   flat   part   gets   bent   up   then   it   becomes   solid geometry.   Normally   our   blueprints   are   describing   a   part   that   is   going to   be   solid   geometry,   but   since   they   are   drawn   on   flat   pieces   of   paper they have to define the part using plane geometry. PLANE: In   geometry   a   plane   is   an   even   or   flat   surface.   It has   width   and   length   but   no   thickness.   You   could think   of   one   surface   of   a   flange   on   a   sheet   metal part   as   a   plane.   Where   two   planes   intersect   is   a line.   In   sheet   metal   we   can   see   this   where   two flanges meet. PLANE   GEOMETRY:Study   of   points,   lines,   line   segments,   circles,   arcs   on a flat surface(plane). SOLID GEOMETRY:Study of points, lines, and planes in space. You   may   be   asking   "Why   bother   with   all   these   definitions?"   Well I'll   tell   you   why.   For   one   reason   developing   sheet   metal   into   a   flat pattern   has   everything   to   do   with   math.   When   I   was   in   high   school   I can   remember   trying   to   learn   trigonometry,   but   a   lot   of   it   just   didn't make   sense   to   me.   Until   I   wound   up   in   the   sheet   metal   trade   and started   to   find   out   that   without   knowing   trig   there   were   some   jobs   I just   couldn't   figure   out.   Someone   showed   me   how   to   use   trig   tables   in a   book   to   figure   out   a   job   one   day   and   I   said   "OH!   That   was   what   they were   trying   to   teach   me   in   High   School".   I   guess   I   couldn't   really understand   trigonometry   until   I   had   something   to   relate   it   to.   This   is called   practical   application.   I   found   out   that   the   more   math   I   knew the   easier   and   faster   my   job   became.   So   just   keep   plugging   away   at this   manual   and   I   will   try   to   use   sheet   metal   parts   in   the   examples and maybe it will all come together for you.
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