In this question, it is given that the diagonal of the board is 18 inches long and one side of the board is 12 inches long.
Let the other side is of length b inches .
Now we use pythagorean identity, which is

Here, a = 12 and c=18
Substituting these values, we will get

And the formula of perimeter is

Substituting the values of the two legs, we will get

Answer:
144°
Step-by-step explanation:
step 1
Find the measure of the central angle of the regular pentagon
Divide 360 degrees by 5 (the number of sides)

Let
c----> the center of the pentagon
we know that
m∠ECA=72°
m∠ACB=72°
therefore
m∠ECB=m∠ECA+m∠ACB
substitute the values
m∠ECB=72°+72°=144°
The measure of angle ECB is equal to the degrees that the pentagon rotate
Answer:
I think it's C but I might be
Step-by-step explanation: