Suppose we want to draw a line with slope `2`. Then we need only mark a point `P`, move one unit to the right, move up two units, and mark a second point `Q`. The line connecting these two points (see Figure A1) has the desired slope. In Figure A2 we draw the line with slope `-1//2 text(.)` The two lines drawn in are perpendicular.
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| Figure A1 A line with slope 2 | Figure A2 A line with slope -1/2 |