Headline Story
Fun with Algebra, #1
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Introduction
Suggest that students sketch possibilities on paper or dry erase boards. Emphasize that they may estimate the angle measurements, taking care to notice whether the angles are acute, obtuse, or right.
Headline Story
None of the other angles in the quadrilateral ABCD are larger than angle B. Angle A and angle C are congruent, and angle D is a right angle. What can you say?
Possible student responses
- Quadrilateral ABCD could be a rectangle; then all of the angles would be 90o.
- Angle B cannot be acute, because if it was, then angle D will be larger than it.
- If angle B is a right angle, ABCD has to be a rectangle.
- If angle B measures 110o, then angle B and angle D together measure 200o, and angle A and angle C have to measure 80o each so that the total for all four angles is 360o. This is how ABCD could look.
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