This pattern won't make a triangle, more like a square. So if you want to start at the tip of one, then CO 3, knit 1 row, then k1 YO, k2 on the next. Do alll WS rows as k1 YO knit the rest of the row, and the RS rows would be k1 YO *k2tog, yo* to the end of the row and k1, repeating the (k2tog yo) sts. Keep alternating a yo knit row with the pattern row until it's as large as you want.
sue- knitting heretic