In quadrilateral ABCD, angle ADB = angle ABC = 90, and A and C are on opposite sides of BD. If AB = 13, AD = 5, and CD = 20, then find AC.
+1253 Draw a diagram, and get that DB=12 and CB=16 by Pythagoras.
Then we want to calculate the length of AC, which we can by observing right triangle ABC where AC is the hypotenuse.
16^2+13^2=425, so the answer is the sqrt of 425, or 5sqrt17.
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