In trapezoid ABCD (AD parallel to BC) BC = 6cm, AD = 14cm, AC = 15cm. E is the intersection of AC and BD. Find CE.

Consider triangles BCE and ADE, in which the angle BEC = AED as vertical angles, the angle CBE = ADE as criss-crossing angles at the intersection of parallel BC and AD of the secant BD. Then the triangles BEC and CED are similar in two angles.

From the similarity of triangles it follows that: BC / AD = CE / AE.

Let the length of the segment CE be equal to X cm, then AE = (15 – X) cm.

BC / AD = 6 * 14 = X / (15 – X).

14 * X = 90 – 6 * X.

20 * X = 90.

X = AC = 90/20 = 4.5 cm.

Answer: The length of the CE segment is 4.5 cm.



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