CAD software is the tool with design indispensable work, regard the homebred CAD that applies more and more extensively in recent years as software, CAD hoped to provide the means of object of circle of 6 kinds of scale in its newest 2009 edition in. But among day-to-day work and study, often be the specific measure that does not know a circle, namely so called straight (half) of diameter, and the circle that just knows to beg and certain and specific target have some to plant locally relation: Mix for example what object is tangent; What to perhaps cross to be nodded foregonely. The order drawing a circle that says to often be used so basically is tangent, round magic art of tangent, tangent painting and painted round way at 3 o'clock. Graph 1 in the command drawing a circle that looks at CAD pursues sketch map of 2 plot task 3 3 circles are tangent and this plants some moment specific locally the relation concealments quite again, this needs us to disentomb well from inside foregone condition hidden condition. We see a example below, in in master adroitly through this example, hoping CAD 2009 painted round way at 3 o'clock hang down dot application. Example is: Beg the radius of gules circular arc according to foregone condition. Foregone condition: Line end length is 10, it is 60 ° with horizontal way included angle, an end points is located in a dot (25, on 20) ; Foregone round diameter is 30, the centre of a circle is located in a dot (50, 60) . Beg: The radius of gules circular arc. (Gules circular arc and mix point-blank round at the same time tangent, and cross line segment the end points of 10 upper part) analyse this title above all, be informed place to beg circular arc to want to be mixed with line segment by the title foregone circle at the same time tangent. What think of more easily so is the tangent, tangent, tangent picture that CAD2009 looks at in using round law. But have two as tangent as its boy or girl friends only. Look again carefully " and cross line segment the end points of 10 upper part " , showing the point of contact that seeks circular arc and line segment is the end points of this upper part, the centre of a circle that is informed place to beg circular arc then is in for certain with line segment 10 perpendicular and on the vertical line that crosses upper part end points, can do vertical line BC then. So come for mirror line with BC foregone circle got the mirror the 3rd tangent target, right now, OK very natural use round method of tangent, tangent, tangent picture. If pursue 3. Clip of will spare finally part is deleted, get radius is what begging circular arc 43.

34. The 2nd kind of method is used namely painted round way at 3 o'clock, also be a method that I consider to introduce in this essay focal point. From foregone can know two nod clearly: With the end points of the point of tangency of foregone circle and line segment. So still one is nodded, be also the most crucial how is the dot found? The centre of a circle that said to beg a circle in front is for certain on vertical line BC, then we can be used hang down sufficient catch BC line segment to get the 3rd is nodded. If pursue 4. Graph 4 hang down sufficient the label with catch 3 to nod clear in the graph also comes out. Very apparent, to this example, painting round magic art should compare tangent, tangent, tangent standard at 3 o'clock more convenient, because do not need a mirror the auxiliary measure such as foregone circle. Be in before, I am used when the picture is round at 3 o'clock, basically think to must want the place that 3 are crossed by the circle. Believe a lot of people can think so. However, through this example we can discover: The practical function of CAD2009 looks in using, want to two are nodded only actually, what can decide the centre of a circle is in again is linear (use namely hang down the dot catchs place of the centre of a circle to get point-blank at 3 o'clock) , also can use painting round magic art undertook drawing a circle at 3 o'clock. The economic performance of CAD 2009 looks in hoping this article can make everybody realises, realise to CAD2009 looks in using, in painting round way at 3 o'clock, "Hang down dot " it is a very useful feature is nodded. CNC Milling