TRIANGLES

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Across
  1. 5. At right angles to a given line or surface
  2. 6. Having the same ratio between corresponding sides
  3. 8. The point where two sides of a triangle meet
  4. 10. Father of geometry who gave a theorem on proportionality
  5. 11. Greek mathematician who proved a famous theorem
  6. 12. Perpendicular dropped from a vertex to the opposite side
Down
  1. 1. Having the same shape and size
  2. 2. Having the same shape but not necessarily size
  3. 3. Ratio of corresponding sides in similar figures
  4. 4. Longest side of a right-angled triangle
  5. 7. Line from a vertex to the midpoint of the opposite side
  6. 9. Point exactly halfway along a segment