Find the area of a square if its diagonal is 20.

1. Vertices of the square – A, B, C, D. Diagonal AC = 20 units. S is the area of the square.

2. We take as x the length of the side of the square.

3. Considering that the sides of the square are equal, we compose the equation:

х² + х² = АС² = 20² = 400 units of measurement².

2x² = 400 units of measurement².

х² = 200 units of measurement².

x = √200 = √100 x 2 = 10√2.

Each side of a square is equal to 10√2 units of measurement.

4. S = х² = 200 units of measurement².

Answer: S equals 200 units².



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