Iris noticed that in an obtuse triangle the obtuse angle always seems to be much
larger than the two acute angles. She wrote a hypothesis that in an obtuse triangle, the sum of the
sizes of the two acute angles is always less than the size of the obtuse
steps Iris uses to check her hypothesis.
She concludes that her hypothesis is correct, because obtuse
angles are always greater than 90°.
She measures the triangles acute
She sums the two acute angles in each triangle. The sum is less
than 90° for all six triangles.
She draws six different obtuse