1. Geometric Constructions with Understanding **This is meant as a resource to the teacher! It is NOT intended to replace teaching in the classroom OR the discourse that should take place!! Inscribing in a Circle

2. Inscribe a Hexagon in a Circle We will inscribe a regular hexagon in the circle. Inscribe means that the regular hexagon’s vertices (corners) will lie on the circle and the regular hexagon will be inside the circle. A regular hexagon has 6 sides where all are the same length & the angles are all the same measure. A regular hexagon is also made up of 6 equilateral triangles. Start with any circle. Make sure you mark your center and a radius.

3. Inscribe a Hexagon in a Circle Segment AB is a radius of circle A.

4. Inscribe a Hexagon in a Circle Construct circle B with radius AB.

5. Inscribe a Hexagon in a Circle Find the points of intersection of circles A & B.

6. Inscribe a Hexagon in a Circle Segment BC and segment BD are congruent to segment BA because all are radii of circle B.

7. Inscribe a Hexagon in a Circle Hide circle B. Construct Circle C with radius CB.

8. Inscribe a Hexagon in a Circle Segment CE and segment CA are congruent to segment CB because all are radii of circle B.

9. Inscribe a Hexagon in a Circle Hide circle C. Construct Circle E with radius EC.

10. Inscribe a Hexagon in a Circle Segment EF and segment EA are congruent to segment EC because all are radii of circle E.

11. Inscribe a Hexagon in a Circle Hide circle E. Construct Circle F with radius FE.

12. Inscribe a Hexagon in a Circle Segment FG and segment FA are congruent to segment FE because all are radii of circle F.

13. Inscribe a Hexagon in a Circle Hide circle F. Construct Circle G with radius GF.

14. Inscribe a Hexagon in a Circle Segment GD and segment GA are congruent to segment GF because all are radii of circle G.

15. Inscribe a Hexagon in a Circle Hide circle G.

16. Inscribe a Hexagon in a Circle Segment AD is a radii of circle A and therefore it is congruent to all the other radii of circle A.

17. Inscribe a Hexagon in a Circle Hide all radii of circle A and you are left with a regular hexagon inscribed in circle A.

18. Inscribe an Equilateral Triangle in a Circle An equilateral triangle has all 3 sides the same length & all 3 angles the same measure of 60 degrees. Normally, we would start with a circle making sure you mark the center and a radius. Because we have already inscribed a hexagon in a circle, we can start with that.

19. Inscribe an Equilateral Triangle in a Circle

20. Because we have a regular hexagon, we know that that angle EFG, GDB, and BCE are congruent (120 degrees).

21. Inscribe an Equilateral Triangle in a Circle We can simply connect every other point on the circle.

22. Inscribe an Equilateral Triangle in a Circle By SAS congruence we have congruent triangles EFG, GDB, and BCE.

23. Inscribe an Equilateral Triangle in a Circle By CPCTC, segments EG, GB, and BE are congruent.

24. Inscribe an Equilateral Triangle in a Circle Hide the hexagon and we are left with an equilateral triangle.

25. Inscribe a Square in a Circle A square has all 4 sides the same length & all 4 angles the same measure of 90 degrees. Start with any circle. Make sure you mark your center and a diameter.

26. Inscribe a Square in a Circle Segment BC is a diameter of circle A.

27. Inscribe a Square in a Circle Construct the perpendicular bisector of diameter BC.

28. Inscribe a Square in a Circle Segments AB, AD, AC, & AE are all congruent because they are all radii of circle A. Angles BAD, DAC, CAE, & EAB are all congruent because they are all 90 degrees.

29. Inscribe a Square in a Circle We can construct segments BD, DC, CE, & EB.

30. Inscribe a Square in a Circle We now have 4 congruent isosceles triangles – BAD, DAC, CAE, & EAB by SAS congruence.

31. Inscribe a Square in a Circle By CPCTC, segments BD, DC, CE, & EB are congruent. Now, we know we have a rhombus inscribed in our circle. To prove it is a square, we have to prove that the angles are 90 degrees.

32. Inscribe a Square in a Circle In an isosceles triangle, the base angles are congruent. The non-base angle is 90 degrees meaning that the two base angles equally share 90 degrees. So, they are all 45 degree angles.

33. Inscribe a Square in a Circle Each vertex on the circle is composed of two 45 degree angles making them each 90 degrees and therefore, a square.