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Copy and Construct (Posted on 2018-12-20) Difficulty: 3 of 5
ABCD is a quadrilateral with AD = BC, AB = 40, CD = 20 and ∠A + ∠B = 90. Find the area of the quadrilateral.

No Solution Yet Submitted by Danish Ahmed Khan    
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re: Solution | Comment 2 of 6 |
(In reply to Solution by Jer)

Calling E the intersection point of lines AD and BC. Looking the figure on the basis of the data you see that ECD angles are 90 45 45. As CD =20 then EC=ED=10sqr2

Then 

AE=AD+ED=40cos(a) [a angle A]
BE=BC-EC=40sen(a)

Easely AD=10sqr6 a=15°
The Area ABCD is then 300

Edited on December 20, 2018, 6:16 pm
  Posted by armando on 2018-12-20 18:15:39

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