+713 Let $ABCD$ and $BEDF$ be two $8 \times 9$ rectangles that overlap, as shown. Find the area of the overlap.
+1365 Ok, let's first let the intersection of AD and FB be Z.
We know AB = 8.
Lets let FZ = x
From the problem, we can tell that triangles ZFD and ZAB are congruent triangles. From this, we know FB = 9.
ZB = FB - FZ = 9 - x
Now, let's use the awesome pythaogrean theorem.
\(ZB^2 = FZ^2 + AB^2 \\ (9 -x)^2 = x^2 + 8^2 \\ x^2 - 18x + 81 = x^2 + 64 \\ 81 - 64 = 18x \\ 17 = 18x \\ x = 17/18\)
Now, we can find the non-shaded area.
\(4 * [ ABZ ] = 4 (1/2) (AB)(AZ) = 4 (1/2) (8)(17/18) = 272/18 = 136/9\)
Now, the shaded area is \(8*9 - 136 / 9 = 72 - 136/9 = 512 / 9\)
Thanks! :)
