People are giving you mathematical solutions to finding the angles of the triangle, however, you are probably looking for the angles to cut boards that will meet in the center of the peak. Similar to cutting rafters on a house. This is entirely different, you want to bisect the peak angle not cut what it is in total.
This is simple with a carpenter's framing square. These are the large squares with a 16" leg and a 24" leg. Divide the 7' width by 2, = 3.5'. Use either the two outside edges or the two inside edges of the square, don't use outside on one and inside on the other. Align the 3.5" mark on the short edge of the square with the bottom edge of the board and align the 7" mark on the long edge of the square, same edge of the board. Draw a line on the long edge, this is the bisect cut for the peak, (plumb cut). Now, make a mark along the short edge of the square, this is the level, (seat) cut at the bottom of the board. It can help with visualization if you choose the top edge of the board you want to use and hold it roughly on the angle you want in front of you as though you are looking on the end of the triangle. It will be easy to see that you need a plumb cut and a seat cut and how those relate to the square and the board. Be careful with some framing squares, one edge might be marked in 10ths or metric, use the edges with inch marks.