In trapezoid ABDC, AB = 5, DC=11. E is the midpoint of AB. F is the midpoint of DC. ∠D+∠C=90∘ . What is the length of EF?
+1486 Let the angle C be 60º, and the angle D be 30º
The height of the trapezoid we may denote with an h
AB = 5 CD = 11 EG = 1.5
h / tan(60º) + h / tan(30º) = 6 ( 11 - 5 = 6 )
h / 1.732 + h / 0.57735 = 6 ( simplify )
0.57735 * h + 1.732 * h = 6
2.3094 * h = 6
h = 2.598077423
EF = sqrt ( h² + 1.5² ) = 3 
