Geometry Proofs

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Across
  1. 1. If a=b then a may be replaced by b in any expression or equation.
  2. 6. If a=b, then ac=bc
  3. 7. If a=b, then b=a
  4. 9. If a=b, then ac=bc
Down
  1. 2. If a=b, and b=c, then a=c
  2. 3. For any real number a, a=a
  3. 4. If a=b, then a-c=b-c
  4. 5. If a=b, then a+c=b+c
  5. 8. a(b+c), then a(b+c)=ab+ac