Curve along two edges on plane I'm new to Blender (v2.77) and I'm working on an automobile door window.

I have a plane where I'd like to create a curve for the window connected to two edges.



Ideally, as seen in the photo, "A" &amp; "B" edges would be removed and the black line would be the new curve.

I tried beveling the vertex at the intersection but naturally, it creates a diamond pattern rather than making a curve between the A+B edges.

Thank you for reading and I appreciate your help!
Extrude whole selection

Delete inner segments and bridge gap

Now bevel edge and delete excess afterwards. 

Follow up with an n-gon or grid fill.