Mathematical mystery

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Across
  1. 4. the another name of the height
  2. 7. the longest side of the right triangle
Down
  1. 1. a kind of quadrilateral has four equal sides and right angle
  2. 2. to make easier
  3. 3. the distance around a triangle
  4. 5. a kind of quadrilateral has only one pair of parallel sides
  5. 6. to find the solution