Ucancam provides the precise coordinates input. We may use the absolute coordinate or the relative coordinate when drawing .The origin (0,0) locates at the center of the page.
The absolute coordinates use the X direction and the Y direction values (from the current spot to the origin) to decide a spot (a, b).
The relative coordinates use one existing spot (not the origin) as reference to define the other as (ra, b): r stands for relative coordinates; a: the value of distance between the two spots in the X direction; b: for the value of the distance between the two in Y direction.
Polar coordinates define a point with distance between the origin and the specified point, and the angle (taking the X-axis positive direction as zero, rotating counterclockwise, when to the specified point, the angle forms) as (a<α): a is for the value of distance;α is the angle value. If the relative polar coordinates is used, it shall be (ra<α).
Coordinate values like a, b may be indicated with digits or mathematical expressions such as (a*sin(α)，b*cos(α)), taking the rectangle-drawing as an example: