Mathematics crossword

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Across
  1. 3. Terms that are separated by + or - signs
  2. 4. a quantity that can be changed and not fixed
  3. 6. a part sloping upwards or downwards
  4. 7. perimeter of a circle
Down
  1. 1. contains two straight lines intersecting at a right angle
  2. 2. The side of a right angled triangle that is opposite to the right angle
  3. 5. The side across from the hypotenuse
  4. 8. Circles which has the same centre