414,395 views
33 votes
33 votes
What are the steps for constructing an inscribed circle in using only a compass and a straightedge?

User BryanMinorPhD
by
2.6k points

1 Answer

6 votes
6 votes

Answer:

Step 1: Place the compass needle on vertex A, adjust the width of the compass to a medium setting, and draw one arc on line segment AB and one on line segment AC.

Step 2: Place the compass needle on the point where the arc intersects line segment AB and draw an arc inside the triangle. Without changing the compass setting, place the compass needle on the point where the arc intersects line segment AC; draw another arc intersecting the arc already inside the triangle. Label the point of intersection P.

Step 3: Draw line segment AP. This is the angle bisector of angle A.

Step 4: Place the compass needle on vertex C, adjust its width to a medium setting, and draw arcs intersecting line segment BC and line segment AC.

Step 5: Place the compass needle on the point where the arc intersects line segment BC, and draw an arc inside the triangle. Without changing its setting, place the compass on the point where the arc intersects line segment AC; draw another arc intersecting the arc already inside the triangle. Label the point of intersection Q.

Step 6: Draw line segment CQ. This is the angle bisector of angle C.

Step 7: Label the intersection of the angle bisectors M. This is the center of the inscribed circle.

Step 8: Place the compass needle on M, and draw two arcs on line segment BC.

Step 9: Place the compass needle on one of the points where an arc intersects line segment BC, and draw an arc outside the triangle; repeat from the point where the other arc intersects line segment BC to create two intersecting arcs outside the triangle. Draw a line from M passing through the point of intersection outside the triangle. This is a perpendicular line from M to line segment BC. Mark the point where the line intersects line segment BC, and label it N.

Step 10: Place the compass needle on M, set its width to N, and draw a circle. This is the inscribed circle of triangle ABC.

User Bharat Vasant
by
2.7k points