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What is the area, in square feet, of an isosceles triangle whose vertex angle is 120 and whose base is 20 feet long? Express your answer as a common fraction in simplest radical form.

 

If you decide to help, I appreciete it

 Jul 25, 2019
 #1
avatar+771 
+2

it seems i am the only one on so ill try but i do not know what the vertex angle is can you infom me on that?

 Jul 25, 2019
 #2
avatar+142 
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It is 120. :D

KeyLimePi  Jul 25, 2019
 #3
avatar+771 
+2

how do you figure that key

travisio  Jul 25, 2019
 #4
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i wrote it in the instructions

Guest Jul 25, 2019
 #5
avatar+8724 
+6

Draw a height from the base to create two congruent 30-60-90 triangles.

 

 

the side across from the  60°  angle  =  10

the side across from the  30°  angle  =  10/√3

 

area of isosceles triangle  =  ( 1/2 )( base )( height )

area of isosceles triangle  =  ( 1/2 )( 20 ft )( 10/√3 ft )

area of isosceles triangle  =  100 / √3     square feet

area of isosceles triangle  =  100√3 / 3   square feet

 Jul 25, 2019

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