<|im_start|>system
You are a helpful assistant. You first think about the reasoning process in the mind and then provide the user with the answer. You should try to truely solve the question by yourself without cheating.  <|im_end|>
<|im_start|>user
 In trapezoid \(ABCD\), \(AB \parallel DC\), \(\angle ABC = 90^\circ\), and \(E\) is the midpoint of leg \(AD\). If \(EC = \sqrt{13}\) and \(AB + BC + CD = 2\sqrt{26}\), then calculate the measure of \(\angle BCE\) in degrees. Show your work in <think> </think> tags. And return the final answer in <answer> </answer> tags.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>
user
45
In trapezoid \(ABCD\), \(AB \parallel DC\), \(\angle ABC = 90^\circ\), and \(E\) is the midpoint of leg \(AD\). If \(EC = \sqrt{13}\) and \(AB + BC + CD = 2\sqrt{26}\), then calculate the measure of \(\angle BCE\) in degrees.
test