How do you draw two lines that meet at right angles?

Answer 1

You need a compass, the little protractor-like device for scribing a circle, and a straightedge. First you draw a straight line. Then, you mark where you want the two lines to cross. You take the compass, put the point on the mark, and swing the compass, making two marks on the line, equidistant from the first mark (the future intersection). Then, you open up the compass a little wider than it was, put the point on one of the second marks, and swing another circle in the area perpendicular to the line. Carefully maintaining this current opening on the compass, pick it up, put the point on the remaining second mark, and swing an arc that intersects the line(s) you just made. You should now have a straight line with two intersecting arcs beside it. Take a straightedge and line up the intersecting points on the arcs. It should go right through the first mark you made on the line. Scribe the line. You now have two lines that meet at right angles.

You can also make one with a right triangle. First you draw a straight line. Then you mark where you want the lines to cross. Then you turn the triangle and put the outside point of the 90° angle up against the point on the line, with one side of the triangle flat against the line. Holding the triangle firmly against the paper, draw part of the intersecting line using the edge of the triangle that's pointed away from and perpendicular to the line. Turn the triangle so that the hypotenuse is lined up with the line you just made and also crosses the first line. Scribe the line. You now have two lines that meet at right angles.