Question 1174735
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Hi
The <u>length</u> of the diagonal of a square is 20
  s^2 + s^2 = 20^2      |Pythagorean Theorem
     2s^2 = 400
      s^2 = 200
       s =  10√2 units   (tossing out negative solution for length)

Wish You the Best in your Studies.
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