Step 1:

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The decorative window is in the shape of a square with a semi circle on top.

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The side of the square is $\"\"$ .

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$\"\"$

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The side of the square is diameter of the semi circle.

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The radius of the semi circle is $\"\"$ .

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The area of the semi circle is $\"\"$ .

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Substitute $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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The area of the semi circle is $\"\"$ .

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The area of the square is $\"\"$ .

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Substitute $\"\"$ .

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$\"\"$

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$\"\"$ .

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The area of the square is $\"\"$ .

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The area of the decorative window is $\"\"$ .

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Substitute $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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The area of the decorative window is $\"\"$ .

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Solution:

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The area of the decorative window is $\"\"$ .