a=152.4cm b=same c=118.11cm Now I need the angles.

I'm building a chicken coop and can't figure out the the angles. I guess two semesters of algebra and trig two years ago doesn't do me any good now if I don't remember any of it. I think the problem is not remembering my calculator functions. I got 0.3875 for A, and I think I just need to hit COS but when I do it doesn't sound right. Maybe I'm way off. Anyway if someone could show their work I'd like to know where I went wrong.

Thanks alot for the help.

Edit:I'll try to show my work below to see where I went wrong.

,so