How can I draw a trapezoid?

[hkBattousai]

I want to draw a trapezoid like shown by the blue lines in the figure. I have two problems drawing it:

1. If I use "Line" tool, the starting point and the final point does not snap each other (Since I'm placing points manually).
2. I don't know how to specify the angle 135°. I used "Smart Dimension" tool, but couldn't find a way to do it. I'm trying to catch that value by altering line lengths but it takes too much time and effort, it has to have another simple solution.

Can you please help me on this two matters.

I'm a newbie.
Using: SW 2010.

 

[gupta9665]

Check this video if it helps Trapezoid