We have a 3-4-5 right triangle and a similar triangle with a hypotenuse of 3 units.
The longer leg of a smaller triangle: 3 / b = 5 / 4 b = (3 * 4) / 5 This is the width of the rectangle.
The length of the rectangle: a = 5 - sqrt( 3² - b² ) 
+14913 Find the shaded area.
\(x:3=3:\sqrt{3^2+4^2}\\ x:3=3:5\\ 5x=9\\ x=\frac{9}{5}\) \(the\ section\ at\ the\ bottom\ left\)
\(b:3=4:5\\ b=\frac{12}{5}\) \(width\)
\(a=5-x=5-\frac{9}{5}\\a=\frac{16}{5}\) \(length\)
\(A=a\times b\\ A=\frac{16}{5}\cdot \frac{12}{5}\)
\(A=\frac{192}{25}=7.68\)
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