## version 1.4 [19.09.2020]

- added new chapters:
- Phantom Points (Chapter 11)
- Isogonal Lines (Chapter 24)
- Isogonal Conjugates (Section 24.1)
- Isogonal Lines Lemma (Section 24.2)
- Parallelogram Isogonality Lemma (Section 24.3)

- Apollonian Circles (Chapter 26)

- added new sections:
- Angle measure of an arc (page 38)
- Ptolemy's Theorem (Section 10.7)
- Fermat Points (Section 10.9)
- Pappus' Theorem (Section 15.4)
- Pole-Polar Duality (Section 21.1)

- added a link to an AoPS forum for discussing the unsolved problems from this book
- added new properties in different chapters (Properties 10.3.4, 10.4.3, 25.2.6)
- added 24 new solved examples in Chapters 1-5 for better onboarding experience
- added 52 new unsolved problems (exact list at the end of the book)
- reordered the Chapters for better learning experience
- minor:
- added more elementary proofs for the properties in Section 19.1
- added a more beautiful proof of Property 10.3.1
- added an alternate proof of Property 10.6.1

- technical:
- corrected the wrong usage of Example instead of Property in many places
- corrected the wrong usage of opening quotation marks in LaTeX
- fixed equations that were split in two lines in a paragraph

## version 1.3 [21.09.2018]

- added new sections in the chapter "Inversion" (18.1 sqrt(bc) Inversion and 18.2 sqrt(bc/2) Inversion)
- added a new chapter about Mixtilinear & Curvilinear Incircles (Chapter 17)
- added a new chapter about Spiral Similarity (Chapter 21)
- added 50 new unsolved problems (exact list at the end of the book)

## version 1.2 [28.07.2018]

- added 50 new unsolved problems (exact list at the end of the book)
- added a new section in the chapter "A Few Useful Lemmas" (10.9 HM Point)
- added a new well-known lemma (Example 16.3 Midpoint of the altitude)
- added a new approach for proving Collinearity (8.2 Parallelogram Trick)
- added a new approach for proving Concurrence (9.4 Concurrent Perpendiculars)
- added a solved example with 4 different proofs in the chapter Symmedian (Example 15.1)
- added visual mnemonic for remembering the ratios in Menelaus' / Ceva's Theorem and the intersections in Pascal Theorem
- restructured the chapters a bit, now the book can roughly be divided in two parts:

Junior (first 10 chapters) and Senior (the other 12 chapters)

## version 1.1 [01.07.2018]

- added 44 new unsolved problems (exact list at the end of the book)
- added a new well-known property in the chapter "A Few Useful Lemmas"
- added a few new solved examples in the chapter "Angles of a Transversal"
- fixed minor mistakes and typos