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# triangle question

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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
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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

!

Jan 26, 2021
#2
+1032
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Hello, Guest!

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

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

Jan 27, 2021