If the diameter of the circle is 42 cm, then the area of ​​the shaded area is​

9514 1404 393

  781.4 cm²

Step-by-step explanation:

The shaded region consists of four (4) 30° sectors and eight (8) 60° segments. The formulas for the areas of these figures can be used.

  area of sector = (1/2)r²θ

  area of segment = (1/2)r²(θ -sin(θ))

For radius r, the area of the 4 sectors is ...

  sector area = 4(1/2)(r²)(π/6) = (π/3)r²

and the area of the 8 segments is ...

  segment area = 8(1/2)(r²)(π/3 -sin(π/3)) = 4r²(π/3 -√3/2) = (4/3)πr² -r²(2√3)

So, the total shaded area is ...

  shaded area = r²(π/3 +4π/3 -2√3)

The radius of the circle is 21 cm, so the shaded area is ...

  (21 cm)²(5π/3 -2√3) ≈ 781.4 cm²

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