Hello!

I'm building a wooden gate for a dog pen and the slope of the ground is about 9 degrees. I'm wanting to cut the 2X4's at 45 degree angles but because it isn't a perfect square, I have the following angles:

Top left - 81 degrees
Top right - 99 degrees
Bottom left - 99 degrees
Bottom right - 81 degrees

I'm just not sure how to cut each 2X4 so that the angles match up perfectly. I've attached a drawing that I hope will help.

Thanks for the assistance!