finding missing angles
Jill: Oh, good point. Could we add a line of our own and chop the room into two
triangles like this?
Joe: How on earth does that help?
Jill: Well…at least we know that angles in a triangle add up to 180 degrees. So if
we make triangles out of the room, we can keep going like we have been. In fact,
there’s another shape with four sides there that could help us with angle 3—we
could divide that into triangles as well maybe? Like this?
Joe: OK, but that seems like a lot more work. Maybe we could try that
thing we did with the paper triangle? With the corners? That might show
us something about four-sided shapes in general, and we can use that to
find those missing angles?
What is it that you need to find out about four-sided shapes in
order to find the missing angles?
See whether you can figure it out, either by adding up the
angles using two triangles, or tearing the corners from a four-
sided shape to see what they add up to.
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