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- ************************* ELLIPSES ************************
- \
- THE ELLIPSE FUNCTION IS ONE OF THE GEOMETRIC SHAPES THAT CAN
- BE GENERATED. LET US SELECT THE FUNCTION "ELLIPSE" FROM THE
- CONSTRUCTION AREA MENU.
- <end>
- THE DEFAULT OPTIONS OF "CE 1P" (CENTER TO ONE POINT) AND
- "ISOMT" (ISOMETRIC ELLIPSE) ARE PRESELECTED. WITH THE
- CURRENT SETTING LET US DRAW A GREEN ELLIPSE FROM ITS CENTER
- TO ONE POINT ON THE CIRCUMFERENCE USING "CE 1P".
- <end>
- THE OPTION "ISOMT" REFERS TO THE RATIO OF MAJOR TO MINOR
- AXES OF THE ELLIPSE. THE RATIO OF MAJOR TO MINOR AXIS CAN
- BE SET AS DESIRED USING THE OPTION "RATIO".LET US SELECT IT.
- <end>
- A POINT HAS BEEN SELECTED ON THE SCREEN WHICH CORRESPONDS TO
- THE INTERSECTION OF THE TWO AXES. FIRST WE SHALL SET THE
- SIZE OF THE MAJOR AXIS BY MOVING THE CURSOR AND ACTIVATING
- IT ANYWHERE ON THE SCREEN.
- <end>
- NEXT LET US MOVE THE CURSOR AND ACTIVATE IT TO SET THE SIZE
- OF THE MINOR AXIS. IF THE MINOR AXIS IS MUCH SMALLER THAN
- THE MAJOR AXIS THE ELLIPSE APPEARS MORE AS A CIGAR SHAPE.
- <end>
- THE RATIO HAS BEEN SET. "ISOMT" HAS BEEN AUTOMATICALLY
- TURNED OFF. LET US DRAW AN ELLIPSE USING THE "CE 1P" OPTION.
- <end>
- LET US CREATE OTHER ELLIPSES WITH DIFFERENT RATIOS.
- <end>
- TO RESET THE RATIO TO ISOMETRIC SELECT "ISOMT".
- <end>
- THE OPTION "1P CE" (1 POINT TO CENTER) DRAWS THE ELLIPSE
- FROM A POINT ON ITS CIRCUMFERENCE TO THE CENTER. LET US TRY.
- <end>
- THE OPTION "ARCS" LETS US DRAW ARCS OF ELLIPSE BY CLIPPING
- THE DESIRED PORTION OF THE ELLIPSE AND ERASING THE BALANCE.
- LET US SELECT "ARCS" AND DRAW AN ELLIPSE
- <end>
- THE ELLIPSE REMAINS IN THE COLOR WHITE. TWO LINES RADIATE
- FROM ITS CENTER. PLACE THOSE LINES ON THE SCREEN AND THE
- COUNTERCLOCKWISE PORTION OF THE ARC BETWEEN THE TWO LINES
- REMAINS ON THE SCREEN AND THE BALANCE IS ERASED.
- HERE IS THE FIRST LINE.
- <end>
- HERE IS THE SECOND LINE.
- <end>
- THE COUNTERCLOCKWISE PORTION OF THE ELLIPSE REMAINS.
- <end>
- "CPYEL" (COPY ELLIPSE) IS A VERY USEFUL OPTION THAT RECALLS
- THE RATIO, SIZE AND THE ROTATION OF THE LAST ELLIPSE AND
- MAKES A COPY OF IT.
- <end>
- LET US SELECT "CPYEL".
- <end>
- NOW ACTIVATE THE CURSOR ANYWHERE ON THE SCREEN.
- <end>
- A COPY OF THE LAST ELLIPSE APPEARS. IT CAN NOW BE PLACED
- ANYWHERE ON THE SCREEN.
- <end>
- THE OPTION "CPYAR" (COPY ARC) PROVIDES A COPY OF THE LAST
- ELLIPSE AND LETS US CLIP THE PORTION OF THE ELLIPSE THAT WE
- WOULD LIKE TO KEEP.
- <end>
- AT ANY TIME THE ON-LINE HELP IS AVAILABLE FOR REFERENCE BY
- PRESSING THE KEY "H" OR "?" WHILE IN ANY FUNCTION.
- <end>
- THE OPTION "CENTR" PLACES A SMALL CROSS AT THE CENTER OF
- THE ELLIPSE FOR REFERENCE.
- <end>
- THE OPTION "UNDO" ERASES THE LAST ELLIPSE.
- <end>
- THE OPTION "CONCN" DRAWS CONCENTRIC ELLIPSES.
- <end>
- *********************** END OF LESSON **********************
- <end>