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  1. The altitudes of a triangle are bisectors in the orthic triangle | plane geometry | intermediate

    The altitudes of a triangle are bisectors in the orthic triangle | plane geometry | intermediate

    14
  2. The chromatic number of a graph and min degrees of its subgraphs | graph theory | intermediate level

    The chromatic number of a graph and min degrees of its subgraphs | graph theory | intermediate level

    13
  3. Segments connecting midpoints of opposite arcs of circumcircle of quadril. | geometry | intermediate

    Segments connecting midpoints of opposite arcs of circumcircle of quadril. | geometry | intermediate

    23
  4. Segments at equal angles from the opposite sides of a cyclic quadrilateral | geometry | intermediate

    Segments at equal angles from the opposite sides of a cyclic quadrilateral | geometry | intermediate

    24
  5. Bisectors of angles between opposite sides of a cyclic quadrilateral | plane geometry | intermediate

    Bisectors of angles between opposite sides of a cyclic quadrilateral | plane geometry | intermediate

    23
  6. Parallelogram formed by midpoints of sides of a quadrilateral | plane geometry | intermediate level

    Parallelogram formed by midpoints of sides of a quadrilateral | plane geometry | intermediate level

    29
  7. The angles between sides of triangle and altitude and circumcenter | plane geometry | intermediate

    The angles between sides of triangle and altitude and circumcenter | plane geometry | intermediate

    33
  8. Reflections of orthocenter with respect to sides of triangle | plane geometry | intermediate level

    Reflections of orthocenter with respect to sides of triangle | plane geometry | intermediate level

    19
  9. Segments between tangency points on opposite sides of a quadrilateral | geometry | intermediate

    Segments between tangency points on opposite sides of a quadrilateral | geometry | intermediate

    23
    1
  10. The tangential quadrilateral formed by centers of 4 tangent circles | plane geometry | intermediate

    The tangential quadrilateral formed by centers of 4 tangent circles | plane geometry | intermediate

    9
  11. A theorem about two circles intersecting on the sides of a triangle | plane geometry | intermediate

    A theorem about two circles intersecting on the sides of a triangle | plane geometry | intermediate

    2
    0
    13
    1
  12. Segments connecting midpoints of opposite sides of a quadrilateral | plane geometry | intermediate

    Segments connecting midpoints of opposite sides of a quadrilateral | plane geometry | intermediate

    16
  13. Tangent lengths to the incircle and the excircle | plane geometry | intermediate level

    Tangent lengths to the incircle and the excircle | plane geometry | intermediate level

    42
  15. Cyclic quadrilateral formed by inscribed angle from the midpoint of an arc | geometry | intermediate

    Cyclic quadrilateral formed by inscribed angle from the midpoint of an arc | geometry | intermediate

    34
  16. Korean Practice; fifth vocab sheet, "intermediate", Part 2

    Korean Practice; fifth vocab sheet, "intermediate", Part 2

    2
  17. The cyclic quadrilateral formed by the external bisectors of a quadr. | geometry | intermediate

    The cyclic quadrilateral formed by the external bisectors of a quadr. | geometry | intermediate

    33
  18. The cyclic quadrilateral formed by the bisectors of a quadrilateral | plane geometry | intermediate

    The cyclic quadrilateral formed by the bisectors of a quadrilateral | plane geometry | intermediate

    15
  19. Korean Practice; fifth vocab sheet, "intermediate", Part 3

    Korean Practice; fifth vocab sheet, "intermediate", Part 3

    2
  20. Deriving Ceva's theorem from Menelaus's theorem | plane geometry | intermediate level

    Deriving Ceva's theorem from Menelaus's theorem | plane geometry | intermediate level

    15
  22. Van Aubel's theorem about cevians | plane geometry | intermediate level

    Van Aubel's theorem about cevians | plane geometry | intermediate level

    31
    2
  23. Korean Practice; fourth vocab sheet, "low-intermediate/beginner", Part 3

    Korean Practice; fourth vocab sheet, "low-intermediate/beginner", Part 3

    3
  24. Deriving Menelaus's theorem from Ceva's theorem | plane geometry | intermediate level

    Deriving Menelaus's theorem from Ceva's theorem | plane geometry | intermediate level

    34