Triangle. Inequalities

Слайд 2

Triangle Inequality Theorem: Can you make a triangle? Yes!

Triangle Inequality Theorem:

Can you make a triangle?

Yes!

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Triangle Inequality Theorem: Can you make a triangle? NO because 4 + 5

Triangle Inequality Theorem:

Can you make a triangle?

NO
because
4 + 5 < 12

Слайд 4

Triangle Inequality Theorem: The sum of the lengths of any two

Triangle Inequality Theorem:

The sum of the lengths of any two sides

of a triangle is greater than the length of the third side.

a + b > c
a + c > b
b + c > a

Слайд 5

Finding the range of the third side: Example Given a triangle

Finding the range of the third side:

Example Given a triangle with

sides of length 3 and 7, find the range of possible values for the third side.
Solution Let x be the length of the third side of the triangle.
The maximum value:
x < 3 + 7 = 10
The minimum value:
x > 7 – 3 = 4
So 4 < x < 10 (x is between 4 and 10.)

x

x

x < 10

x > 4

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Finding the range of the third side: Given The lengths of

Finding the range of the third side:

Given The lengths of two

sides of a triangle
Since the third side cannot be larger than the other two added together, we find the maximum value by adding the two sides.
Since the third side and the smallest side given cannot be larger than the other side, we find the minimum value by subtracting the two sides.

Difference < Third Side < Sum

Слайд 7

Finding the range of the third side: Example Given a triangle

Finding the range of the third side:

Example Given a triangle with

sides of length a and b, find the range of possible values for the third side.
Solution Let x be the length of the third side of the triangle.
The maximum value:
x < a + b
The minimum value:
x > |a – b|
So |a – b|< x < a + b
(x is between |a – b| and a + b.)

x < a + b

x > |a – b|

Слайд 8

In a Triangle: The largest angle is opposite the largest side.

In a Triangle:

The largest angle is opposite the largest side.

The smallest

angle is opposite the smallest side.

The smallest side is opposite the smallest angle.

The largest side is opposite the largest angle.

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Theorem If one angle of a triangle is larger than a

Theorem

If one angle of a triangle is larger than a second

angle, then the side opposite the first angle is larger than the side opposite the second angle.
Слайд 10

Theorem If one side of a triangle is larger than a

Theorem

If one side of a triangle is larger than a second

side, then the angle opposite the first side is larger than the angle opposite the second side.
Слайд 11

Corollary #1: The perpendicular segment from a point to a line

Corollary #1:

The perpendicular segment from a point to a line is

the shortest segment from the point to the line.

This is the shortest segment!

This side is longer because it is opposite the largest angle!