Here's how I would figure it, based on your photo. The shape and size and pattern of your pavers will obviously be a consideration but think of it as two rectangular walkways with a triangle connecting them. Both rectangles meet at one point on one side, the inside of that corner. If you use a framing square from that point, you'll be able to square off the end of each rectangle and then calculate the pie shape section where you'll need to trim pavers to fill it in.
Let's say that the pie shaped area is a 45 degree wedge. Half of that would 22.5 degrees. If you cut your first pavers at 22.5 degrees, both left and right side of the center of the of the wedge, it will get you square to the rectangle sections.
I would also start at that corner because you want to as full a paver as possible.
Sounds complicated but it's not.