Answer:
D,12cm
Step-by-step explanation:
100 percent/TRUST
Answer:
The area of an octagon whose perimeter is 120 cm is 1086.4 
Step-by-step explanation:
An octagon is a polygon with eight sides. If the lengths of all the sides and the measurement of all the angles are equal, the octagon is called a regular octagon.
There is a predefined set of formulas for the calculation of perimeter, and area of a regular octagon.
The perimeter of an Octagon is given by

and the area of an Octagon is given by

We know that the perimeter is 120 cm, solving for side length (a) in the perimeter formula we get

Now, we calculate the area

Answer:
C(x) = 
Step-by-step explanation:
Data provided in the question:
Area of the field = 3600 square feet
Fencing charges = $3.50 per foot
Let the side along the river be 'x' feet and the other side of the 'B'
now,
Area of rectangle = Bx = 3600 square feet
or
B =
feet
and total length to be fenced = x + 2B
therefore,
Total cost of fencing = Fencing charges × total length to be fenced
or
Total cost of fencing = $3.50 × ( x + 2B )
substituting the value of B from (1)
Total cost of fencing, C(x) = 
or
C(x) = 