The perimeter is 21.66
The figure is something like the one that is in the image below:
We want to find the total perimeter of the polygon ABECD
This will be:
AB + BE + EC + CD + DA
Remember that for a triangle rectangle of catheti A and B, the area is given by:
A*B/2
We know that the sides of the triangle rectangle are:
BE, EC, BC.
Because BE = EC, these can not be the hypotenuse of the triangle, then the catheti are BE and EC
Knowing that the area of the triangle rectangle is 8, we can write:
EC*BE/2 = 8
and EC = BE = x
x^2/2 = 8
x^2 = 8*2 = 16
x = √16 = 4
Then the two catheti of the triangle rectangle are 4 units long.
EC = 4
BE = 4
and we know that:
AB = BE = EC
then:
AB = 4
and because this is a rectangle, we also have:
DC = AB = 4
now we want to find the last side of the figure, AD,
Which we already know is equal to the hypotenuse of the triangle.
Remember the Pythagorean's theorem, which says that the sum of the squares of the catheti is equal to the square of the hypotenuse.
Both catethus are equal to 4, then we have:
H^2 = 4^2 + 4^2 = 32
H = √32 = 5.66
then:
DA = 5.66
Now we have:
AB = BE = EC = DC = 4
DA = 5.66
Then the perimeter is:
AB + BE + EC + CD + DA
4 + 4 + 4 + 4+ 5.66 = 21.66
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