Q&A for How to Find the Area of Regular Polygons

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  • Question
    How do I find the perimeter of a regular polygon with one side being 5-2x and another being -4x+9?
    Community Answer
    Since a regular polygon has congruent sides (every side is equal to each other) you set up the equation 5-2x = -4x+9 then you solve for "x". After solving for "x", you substitute the answer you got from "x" back into the one of the expressions from one of the sides. You should get the answer of how many units one of the sides is. After that, just multiply that answer by how many sides the polygon has to get your perimeter.
  • Question
    How do I find the perimeter of a nonagon with area of 28.8 and side length of 21?
    Community Answer
    The perimeter equals the side length times the number of sides. In this case, multiply 21 by 9 and you will get a perimeter of 189.
  • Question
    What is the area of a polygon with sides of 12m, 11m, 3m, and 3m?
    Community Answer
    Since the given measurements of the sides best represents a trapezoid, you use the area of a trapezoid equation A=h*((b1+b2)*0.5) where A is the area, h is the height of the trapezoid, and where b1 is the top base and b2 is the bottom base. To find the height, you subtract b2 by b1, then divide it, then substitute that answer into "a" of the Pythagorean theorem a^2+b^2=c^2, where "c" equals the length of the side of your trapezoid which in this case is 3m. You solve for b in that equation to get your height. Once you got the measurement of the height of the trapezoid, you use the area of a trapezoid equation and substitute your answers in it to get your area.
  • Question
    A regular hexagon is inscribed in a circle having an area of 158 cm^2. How can I find the area of the circle not covered by hexagon?
    Community Answer
    Find the radius of circle using volume of circle formula (pi*(r)^2), which is equal to 158.9 (here, r = 7.09). Radius of circle = length of one of the side of regular hexagon. Then, using the area formula (area=(a*p)/2), calculate its area (here, 130.59).
  • Question
    What is the equation for a regular heptagon?
    Donagan
    Top Answerer
    The only equation is the general equation for any regular polygon as given in Part 1 above.
  • Question
    How do I find the area of a nonagon with a side of four inches?
    Community Answer
    To get the area, multiply the perimeter of the nonagon by the apothem and then divide by 2. You get the perimeter by multiplying 4 by 9, getting 36. The apothem is 4/(2Tan(180/9)), which equals 5.5. Now you get area = (5.5 x 36)/2, which is 99.
  • Question
    If the perimeter of an equilateral triangle is equal to the perimeter of a regular hexagon, what is the ratio of that equilateral triangle to the regular hexagon?
    Community Answer
    To find the answer to this question, I used the formula A=(b^(2)ncos^(2)(180/n))/2sin(360/n) in the which perimeter is bn, so b=p/n. I filled out the formula with the same P in both the triangle's formula and the hexagon's and put in the constant j as the multiple of the two so the area of the hexagon = j x the area of triangle. Eventually I came out with j=1.5, so the hexagon would be 1.5 times the size of the triangle.
  • Question
    How do I find the area with only variables?
    Donagan
    Top Answerer
    If you have no actual numbers to work with, you can't find the area.
  • Question
    How do I find the area of a regular polygon that is square and has a radius of six?
    Community Answer
    Here the diameter (12 units) of the circumscribing circle is the diagonal of the square. Since the diagonal is sqrt(2) = 1.414 times the side of the square, the area of the square is 0.5 * 12 * 12 = 72 sq. units.
  • Question
    How do you find the area of a polygon when the side length is not given?
    Community Answer
    If you know the perimeter, multiply it by the apothem, then divide by two. That equals the area of the polygon.
  • Question
    How do I find the area of a hexagon when I only have the apothem?
    Donagan
    Top Answerer
    You also need the perimeter. See Method 2 in the wikiHow article on how to Calculate the Area of a Hexagon .
  • Question
    How do I find the side length if I'm given the apothem?
    Donagan
    Top Answerer
    You would need more information than that.
  • Question
    How do I find the area of a pentagon without trigonometry?
    Donagan
    Top Answerer
    The general equation for the area of any regular polygon given above does not involve trigonometry.
  • Question
    How do I find the area of a regular octagon with sides 4 cm?
    Community Answer
    Area of an regular polygon is number of sides * length of a side. Number of sides = 8, and one side = 4 cm, therefore area is 8 * 4 = 32 cm.
  • Question
    How do I calculate the length of the apothem of a pentagon if I only have the radius?
    Community Answer
    The radius = 1 side of the pentagon. Use the procedures of finding the value of apothem described above.
  • Question
    How do I find the area of a polygon when I only have the radius?
    Community Answer
    If you mean apothem, rather than radius, refer to method 1. Radius implies a circle. To find the area of a circle, square the radius and multiply by π.
  • Question
    How do I find the apothem of a polygon when I know it's area?
    Community Answer
    Apply the formula that shows how to find the Apothem of Part 2; just ignore the area of the polygon.
  • Question
    How do I find the area of a regular polygon with no side lengths when I have the radius and the apothem?
    Community Answer
    You would need to find one of the angles and use trigonometry to find the length of half the side length, since the apothem bisects the side. Then, you'd use the side length multiplied by the number of sides to get the perimeter, and since A=ap/2, where A is area, a is apothem, and p is the perimeter, you'd plug those in to find the area.
  • Question
    A polygon has 4 sides and each side has 25cm. What is the perimeter of that polygon?
    Donagan
    Top Answerer
    (25 cm)(4) = 100 cm.
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