Answer:
A = P * a / 2
A = 81.25
Step-by-step explanation:
We have that there is a corresponding formula for a regular decagon, which depends on the apothem and the perimeter, it is the following:
A = P * a / 2
In this case, the perimeter is the sum of all the sides, that is, 10 sides, therefore:
P = 10 * 3.25
P = 32.5 meters
We replace:
A = 32.5 * 5/2
A = 81.25
Which means that for that regular decagon, the area is 81.25 square meters.
The different that the number has been changed 90 degree so they have change the negative to positive and positive to negative sign
A = l²
A = 7.2²
A = 51.84
51.84 inches