Answer: 8 Inches
Step-by-step explanation:
First thing we do is to draw an octagon inscribed inside a square, as shown in the picture attached,
The we know one side of the square is 20 inches, and one side consist of the addition of a length of the octagon, and two sides for a right angle triangle, which has the smaller angles inside as 45, 45 degrees making those two sides equal to each other, So to find the value of x which is labeled as the side of the octagon, we adding the two sides of the right angle triangle with the side of the octagon to equate to 20 inches
Since a side of the square is 20inches
From the diagram, y is labeled as the two equal sides of the right angle triangle
So
y + x + y = 20 (1)
Using Pythagoras theorem for the right angle triangle
y2 + y2 = x2
2y2 = x2
y2 = (x2)/2
y = x/root(2)
So putting this in the previous equation (1)
x/root(2) + x + x/root(2) = 20
2x/root(2) + x = 20
2x/root(2) + xroot(2)/root(2) = 20
x(2 + root(2))/root(2) = 20
x(2 + root(2)) = 20(root(2))
x = (20(root(2)))/(2 + root(2))
= 28.2843/3.4142 = 8.2343
So therefore answer is approximately 8 inches