MHB How to Find the Area of Quadrilateral ABCD with Given Side Lengths and Angles?

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To find the area of quadrilateral ABCD with sides AB = 15, AD = 24, BC = 7, CD = 20, and angles ABD + BDC = 90 degrees, one approach involves dividing the quadrilateral into two triangles. By applying the formula for the area of a triangle, the areas of triangles ABD and BCD can be calculated separately. The area of triangle ABD can be determined using the sine of angle ABD, while triangle BCD can utilize the sine of angle BDC. Summing the areas of both triangles will yield the total area of quadrilateral ABCD. This method effectively utilizes the given side lengths and angle relationships to solve the problem.
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$Quadrilateral\,\,ABCD,\overline{AB}=15,\overline{AD}=24,\overline{BC}=7,\overline{CD}=20, \,\,
\angle ABD+\angle BDC=90^o\,\,
find \,\, the \,\, area\,\, \,\, of \,\, ABCD$
 
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My suggested solution:
View attachment 6350$\bigtriangleup BCD$ is replaced by its mirror image $\bigtriangleup BED$. $\angle ABE$ is then $90^{\circ}$.Length of diagonal $d_2$ is: $\sqrt{15^2+20^2} = 25$.The total area of the quadrilateral can now be calculated:Area of $\bigtriangleup ABE$ + Area of $\bigtriangleup AED$ (Herons formula with perimeter $56$) $= 150+84 = 234$.
 

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lfdahl said:
My suggested solution:
$\bigtriangleup BCD$ is replaced by its mirror image $\bigtriangleup BED$. $\angle ABE$ is then $90^{\circ}$.Length of diagonal $d_2$ is: $\sqrt{15^2+20^2} = 25$.The total area of the quadrilateral can now be calculated:Area of $\bigtriangleup ABE$ + Area of $\bigtriangleup AED$ (Herons formula with perimeter $56$) $= 150+84 = 234$.
nice solution !
 
Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?

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