Verify experimentally that in a triangle, angles opposite longer sides are larger, sides opposite larger angles are longer, and the sum of any two side lengths is greater than the remaining side length; apply these relationships to solve real-world and mathematical problems.
Represent constraints by equations or inequalities, and by systems of equations and/or inequalities, and interpret solutions as viable or nonviable options in a modeling context. For example, represent inequalities describing nutritional and cost constraints on combinations of different foods.
Record the length of your short grid strip as the length of segment . Then choose a number between 4 and 10 to record as the length of segment . The values you choose for and can be the same, but no one in your group should have the same values as you do for and . Once you have chosen your value for , draw that length on your graph paper.
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Use your long grid strip to measure different possible lengths for so that and your fixed lengths make a triangle. Include at least one of each of the following, recording your findings below.
obtuse triangle
acute triangle
right triangle
length
length
length
Compare your list of side lengths with those of your group. What observations can you make about the length of ?
1.3
Activity
Standards Alignment
Building On
Addressing
G-GMD.6
Verify experimentally that in a triangle, angles opposite longer sides are larger, sides opposite larger angles are longer, and the sum of any two side lengths is greater than the remaining side length; apply these relationships to solve real-world and mathematical problems.
Represent constraints by equations or inequalities, and by systems of equations and/or inequalities, and interpret solutions as viable or nonviable options in a modeling context. For example, represent inequalities describing nutritional and cost constraints on combinations of different foods.
Use the available tools to figure out if each set of three side lengths could make a triangle.
4, 6, 7
4, 6, 100
4, 6, 6
4, 6, 10
4, 6, 0.5
4, 6, 2
A triangle has two sides that measure 7 and 12.
What is a length for the third side that is too long?
What is a length for the third side that is too short?
What is a length for the third side that would create a triangle?
Student Lesson Summary
Triangles are made up of three sides, but can those side lengths be any values? Can a triangle have side lengths 4, 6, and 100 units? No, because 4 and 6 aren’t long enough to reach the endpoints of a side with 100 as a length.
Another example is 4, 6, and 2 units. To meet at the endpoints, lengths 4, 6 and 2 would form a line segment.
But the side lengths 4, 6, and 8 units will form a triangle.
Verify experimentally that in a triangle, angles opposite longer sides are larger, sides opposite larger angles are longer, and the sum of any two side lengths is greater than the remaining side length; apply these relationships to solve real-world and mathematical problems.