Does the block have a name? If it does try putting the name in a Google search and add rotary cutting and see if a tutorial comes up. Most simple squares and triangles can be rotary cut using your acrylic rulers. If they are half square triangles done in 2 colours, I like to do those as squares. I am not sure but I think it's 7/8 you add to a square if you are going to later cut it into two parts. You put your light square and your dark square, right sides together. You draw a line through the center of the square on the diagonal. You stitch a 1/4 inch seam on either side of the line and then cut them apart on the drawn line. You now have to triangle units. This may work with your pattern or it may be the wrong triangle. Good Luck.