Title: Lesson 11-4
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Last saved by: The McGraw-Hill Companies
Company: DellComputerCorporation

Lesson 10-5 Problem-Solving Investigation

Use Logical Reasoning

Draw an acute triangle.  How can you confirm that it is acute?

UNDERSTAND | Acute triangles have all three angles measuring less than 90°.  You need to find whether the angles drawn are all less than 90°.
PLAN | Draw several acute triangles and measure the angles.
SOLVE | Each of the angles in each of these three triangles is less than 90°.  So, these are acute triangles.
CHECK | Draw a triangle with at least one angle measuring more than 90°.  This will not be an acute triangle.