Determining Triangle Formation from Side Lengths

Miss Lee explains the triangle inequality theorem, which states that the sum of the lengths of any two sides of a triangle must be greater than the length of the third side. She provides multiple examples to illustrate how to determine if three given side lengths can form a triangle. The video includes both valid and invalid triangle examples, and concludes with a problem-solving exercise to find a possible side length that would form a triangle.

What is the main topic of today's lesson?

• Triangle angles

• Triangle perimeter

• Triangle side lengths

• Triangle area

What must the sum of any two sides of a triangle be in relation to the third side?

• Greater than the third side

• Less than the third side

• Equal to the third side

• Not related to the third side

If you have sides of lengths 4, 5, and 7, will they form a triangle?

• No, because 4 + 5 < 7

• Yes, because 4 + 5 = 7

• No, because 5 + 7 < 4

• Yes, because 4 + 5 > 7, 5 + 7 > 4, and 7 + 4 > 5

Given sides of lengths 4, 2, and 7, why can't they form a triangle?

• Because 4 + 2 > 7

• Because 4 + 2 < 7

• Because 4 + 7 < 2

• Because 2 + 7 < 4

For sides 11, 6, and 13, which combination do you check first?

• 11 + 6

• 6 + 13

• 11 + 13

• 6 + 11

If you have sides 5, 15, and 9, which combination fails the triangle inequality?

• 5 + 15 > 9

• 15 + 9 > 5

• 9 + 5 > 15

• None of the above

What should be the length of X to form a triangle with sides 20 and 13?

• 35

• 13

• 25

• 15

Why does the side length 35 not work with sides 20 and 13?

• Because 20 + 13 is not related to 35

• Because 20 + 13 = 35

• Because 20 + 13 > 35

• Because 20 + 13 < 35

Which of the following is true for the side lengths 13, 13, and 20?

• 13 + 13 < 20

• 13 + 13 > 20

• 13 + 20 < 13

• 13 + 13 = 20

What is the final step to check if 13 is a valid side length with 20 and 13?

• All of the above

• Check if 13 + 20 > 13

• Check if 13 + 13 > 20

• Check if 20 + 13 > 13