"My mind has gone blank!" you say?

The problem is a little tricky

Some one might come up with a neater solution.

So I will give you a plan.

1) Draw a diagram!

2) Notice that ABC and BCD are right angled triangles (which are the right angles?)

3) Assuming you know what to do now,are hypotenuses of equal length??

4) Have used the condition that AB || CD ? What can you say about angle CBA and angle BCD? Now what about the remaining angles? Are they equal?

5) We have proved(hopefully you have) some angles equal and some side equal. Which postulate tells you they are congruent?

Answering my questions in the plan,requires little effort.

Hope you get the answer