![]() ( Note: These triangles are not necessarily Δ ABC and Δ A'B'C', since the first arc in the construction need not pass through A and/or C on the given angle. Since the triangles are congruent by SSS and any leftover corresponding parts will also be congruent (by CPCTC), we know that ∠ ABC is congruent to ∠ A'B'C'. These addition of these segments will create two triangles that have 3 sets of congruent (equal) sides. ![]() We know these lengths are the same in both drawings since they represent the measured spans of the same arcs. Proof of Construction: When your construction is finished, draw line segments connecting where the first arcs cross the sides of the angles. Connect this new intersection point to the starting point (dot) on your reference line. Using this width, place the compass point on the reference line where the previous arc crosses the reference line and mark off this new width on your new arc.ĩ. (Place a small arc to show you measured this distance.)Ĩ. Go back to the given angle ∠ ABC and measure the span (width) of the arc from where it crosses one side of the angle to where it crosses the other side of the angle. Without changing the size of the compass, place the compass point on the starting point (dot) on the reference line and swing an arc that will intersect the reference line and go above the reference line.ħ. Swing an arc so the pencil will cross BOTH sides (rays) of the angle.Ħ. Stretch the compass to any length that will stay "on" the angle.ĥ. So if we have a starting point labeled A, by placing a second point B somewhere else, we will be telling the ray. Place the point of the compass on the vertex of the given angle, ∠ ABC (vertex at point B).Ĥ. A ray is a line that starts at one point and continues forever in one direction. Place a dot (starting point) on the reference line.ģ. By copying the circle at A', the radii segments will be congruent.Ģ. A ray is a part of a line that has one endpoint and goes on infinitely in only one direction. Note: You may also think of the length from A to B as being the radius of a circle with center at A. draw some specific optical elements like lenses, (concave, convex) mirrors and do things like above construct automatically virtual images 3D drawings would be fine I would prefer free software for linux. ![]() Since the given segment and the copy are the same length, the segments are congruent. ![]() Proof of Construction: The compass was used as a measuring tool to obtain (and copy) the length of the given segment. Without changing the span of the compass, place the compass point on the starting point (dot) on the reference line and swing the pencil to create an arc crossing the reference line. (This small arc will show that you measured the length of the segment with your compass.)ĥ. Stretch the compass so that the pencil is exactly on B. Place the point of the compass on point A on the given figure.Ĥ. Draw a dot on the reference line to mark your starting point for the construction.ģ. Using a straightedge, draw a reference line, if one is not provided.Ģ. ![]()
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