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					   Solve for x in the following 45-45-
              90 triangles


 10             X                  x
                                               10 3



What is the rule with the 45-45-90 triangle?
              30- 60 -90 Triangle
          A 30-60-90 is an
         equilateral triangle
        that is bisected!! 




Section 5.9
     Triangle ABC is equilateral, and
      CD is an altitude or height.

                            1. What are m A and m  B? _________
 2 cm             2 cm      2. What are m ACD and m BCD? _______

                            3. What are m  ADC and m BDC? _______

                            4. What is the length of AD? ___________
CD bisects ACB             5. How do AC and AD compare?
                            ________________________________


6. Use the Pythagorean Theorem to find the length of the other leg.
Simplify the square root.
A 30-60-90 Triangle is also known as
a bisected equilateral triangle.

           60



       a              2a
                           30

                a 3
  Triangle ABC is equilateral with side
  lengths of 3 in. Find the height, CD .
Step 1: Label the degrees
  of the triangles.
Step 2: Label the sides of
  the triangles.
What is the length of AD ?
  Label AD .
Step 3: What is the length
  of CD ?
     Examples: Find the missing
               sides.

1.                  2.
     Examples: Find the missing
               sides.

3.                  4.
  On your own:
                 7
            60
4 2

 30
                9

                          What happens when
          60
                           you are given the
                             longest leg?

     Find the missing sides in the triangles
     below.
                     b.         c.
a.

                    9 2

               30                        30

         12                          5
                           60
      Extra Practice Problems
30
                            30




           60
                     32               60



      5

 30
                                 30

          10
                     2 20
                                           60
                60
            Examples Continued:
a.   Find the altitude of an Equilateral
     triangle with perimeter 18 feet.




b.   Find the side of an equilateral triangle
     with altitude 6 cm.




                                            SKHmath
               Application:
An ornamental pin is in the shape of an
equilateral triangle. The length of each
side is 6 centimeters. Josh will attach
the fastener to the back along AB. Will
the fastener fit if it is 4 centimeters
long?

				
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posted:9/15/2012
language:English
pages:12