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Triangle ABC is isosceles with AB = BC.  If AB = 20 and [ABC] = 240, then find the perimeter of triangle ABC.

 Jan 26, 2021
 #1
avatar+11086 
+1

Triangle ABC is isosceles with AB = BC.  If AB = 20 and [ABC] = 240, then find the perimeter of triangle ABC.

 

Hello Guest!

 

\(\beta=360°-240°=120°\)

\(b^2=a^2+c^2-2ac\ cos\beta\)

\(b^2=20^2+20^2-2\cdot 20\cdot 20\cdot \ cos\ 120°\)

\(b^2=1200\)

\(b=\sqrt{1200}\)

\(b=34.641\)

\(P=a+c+b=20+20+34.641\)

\(P=74.641\)

 

 The perimeter of triangle ABC is 74.641

laugh  !

 Jan 26, 2021
 #2
avatar+1032 
+2

Hello, Guest!

Your question is no good!!!            [ABC] cannot be more than 200 !!!

 

If [ABC] = 200 then the perimeter is 40 + 5√32  smiley

 Jan 27, 2021

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