Right angled triangle 1- grey: chain 13. Foundation row 13. On return pass of all next rows, decrease on the edge at the end of the return pass. 13 rows. On the forward pass, ignore the second vertical which was joined to the edge stitch. Make second stitch into the third vertical. The right angle is the centre of the block.
Triangle 2- natural. Pick up 13 stitches along the return pass edge of triangle 1. Work rows as in Triangle 1.
Triangle 3- black: same as Tr2.
Triangle 4- grey ragg: begin as for Tr 2&3 on foundation row. Before starting return pass, insert hook into very first chain stitch of Tr1 to link these together. YO and pull through grey chain and first ragg stitch as if they are one. Each row is linked to the next chain in Tr1 at the start of the return pass.
Doing the math: each line from centre to corner has 13 stitches. Each outside edge also has 13 stitches but is much longer than the centre lines.
Next step is finding the increase ratio for the outer edges ie 1.5/1, or 19 stitches. Other options to check out: using a larger hook on 13 stitches to join, or using the same size hook for a sc join.
Photo shows join with 8 mm hook (same size) and sc closure. This does not need extra stitches.
https://en.m.wikipedia.org/wiki/Special_right_triangle
TO MAKE A PLANNED PROJECT, YOU NEED TO DRAW OUT YOUR SQUARES AND COLOUR SEQUENCE. ALL THE SAME SQUARES MIGHT NOT BE WHAT YOU WANT.
Squares are 6.5 inches when finished. Cowl is 26x7 inches with a row of sc around top and bottom edges, also with 8 mm hook.
If squares were smaller, you could make a hat with 1 for the top and 4 around.
Used 8 squares in a row to make a double wrap cowl. Edged with one row of hdc in black.
June 29, 2017: saw a post formthe Purl Soho baby blanket.
https://www.purlsoho.com/create/2016/08/12/knit-four-poin...
Will look at doing this down the road, perhaps in a lacey stitch.