Hi Guys, thx for the previous helpSo far I learned, line, offset, circle, xline and rotate.I don't know how to get "left and right slopes" with 36 degree. My approach was to think them as triangle with 36 degree. So I extend central line and rotate 18 degree to left and right, but it was wrong. please give me help and tipsthank you so much Garyficult with

First.  Are you aware that the default setting for AutoCAD measures angles in a counter-clockwise direction and East happens to be angle zero?Second.  Are you familiar with direct distance entry at the command line?  If I wanted to draw a line 20 units long at a 45 degree angle I would start the line command, pick my start point then type @20<45.Third.  Are you familiar with Polar Tracking or with the SNAPANG command.  Both are other ways to accomplish the same task.

That will be affected by what you use as the base point for the rotation.  If starting at the center-line position, you would need to know the point at which the 36-degree-angle Lines would (virtually) intersect in order to get the right result using Rotate.  In that situation, I would draw Lines vertically from the quadrant points of the Circle, and Rotate each 18 degrees one way or the other, using the center of the Circle as the rotation base point.

oh my gosh, i try both of your methods and then after a moment of truth, yes it work. it work. Is this some kind of math illusion..?i receive like 100 gigabyte of help from you guysthx