Obsessed with Triangles (and math in the real world!)

A couple weeks ago, I attended my first event as a newly minted member of the Baltimore Modern Quilt Guild.  It was a master class about sewing half-square triangles.  I had so much fun learning all the different methods and REALLY wish I’d had some training like this before I sewed Mark’s quilt! I am really happy to be part of this group, to be with a group of women who love fabric and sewing as much as I do!

We were instructed to bring a background fabric along with a variety of prints to make our practice blocks.  Instead, I brought a print that I had gotten on super sale a few weeks ago (Cloud 9 Organics for $3/yard!) and some fun, bright solids from my stash.

011 (1278x1280)

We were given a pattern as part of the workshop fee and I think I will continue to work away at making half-square triangles until I have enough to make the quilt.  It will be a fun one to have around the house, even though it doesn’t really match any of the rest of our decor! 🙂

010 (1280x1280)I’ve been having fun finding new patterns to make with them!


At the workshop, I learned the strip method of piecing half-square triangles.  It was definitely my favorite way out of all the different ways that we tried.  At the workshop, there was some discussion about the math involved in using this technique. You can see one method of figuring it out in this post but I thought I’d share the even more nerdy way below.

triangleAs you can see in the triangle above, if you draw a line from the top of the triangle to the base (this line is the “altitude”), you form not only a right triangle, but a special right triangle, a 45-45-90 triangle.  When that happens, you don’t have to use the long-form Pythagorean theorem to figure out x. Just divide your unfinished dimension (i.e. the x√2 dimension) by √2 to isolate x and you’ll get the amount that you need to cut your triangles! If you want to end up with 3.5″ half-square triangles, you’ll end up with the equation, 3.5=x√2.  Solve for x and you’ll get 2.47, round to 2.5, add 1/2″ for seam allowance and you’ll see that you need to cut a 3″ strip for 3.5″ half-square triangles.

You actually don’t have to remember any of this triangle math if you don’t want to.  Just determine your unfinished dimension, divide by the square root of 2 (which any calculator will let you do) and then add 1/2″ for seam allowances and cut your strips to that width. Ta da!

Or you can just eye it.  But what fun is that when you can put geometry and algebra to good use in real life?

Mrs. Peterson, my high school math teacher, should be so proud of me right now. Having a math-loving husband helps too! 🙂

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