21. Writing Describe three ways to find the area of a regular hexagon if you know only the length of a side.
22. Think About a Plan The surveyed lengths of two adjacent sides of a triangular plot of land are 80 yd and 150 yd. The angle between the sides is 67 ° . 67 degrees .  What is the area of the parcel of land to the nearest square yard?
    • Can you draw a diagram to represent the situation?
    • Which formula for the area of a triangle should you use?

Find the perimeter and area of each regular polygon to the nearest tenth.

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27. Architecture The Pentagon in Arlington, Virginia, is one of the world's largest office buildings. It is a regular pentagon, and the length of each of its sides is 921 ft. What is the area of land that the Pentagon covers to the nearest thousand square feet?

28. What is the area of the triangle shown below?

    

29. The central angle of a regular polygon is 10 ° . 10 degrees .  The perimeter of the polygon is 108 cm. What is the area of the polygon?
30. Replacement glass for energy-efficient windows costs $ 5 / f t 2 . dollars 5 slash f . t squared , .  About how much will you pay for replacement glass for a regular hexagonal window with a radius of 2 ft?
    1. $10.39
    2. $27.78
    3. $45.98
    4. $51.96

Regular polygons A and B are similar. Compare their areas.

31. The apothem of Pentagon A equals the radius of Pentagon B.
32. The length of a side of Hexagon A equals the radius of Hexagon B.
33. The radius of Octagon A equals the apothem of Octagon B.
34. The perimeter of Decagon A equals the length of a side of Decagon B.

    The polygons are regular polygons. Find the area of the shaded region.

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