Math crossword puzzle

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Across
  1. 3. The mathematics of working with variables.
  2. 4. Calculations involving numbers. This typically involves the basic operations addition, subtraction, multiplication, division, and exponents.
  3. 7. A polygon with three sides.
Down
  1. 1. In plane geometry or solid geometry, the bottom of a figure.
  2. 2. A quantity that can change or that may take on different values.
  3. 4. Half the difference between the minimum and maximum values of the range. Only periodic functions with a bounded range have this.
  4. 5. A closed plane figure for which all sides are line segments.
  5. 6. The shortest distance between the base of a geometric figure and its top, whether that top is an opposite vertex, an apex, or another base.