Answer: 942 - 225*sqrt(3)
This is roughly equivalent to 552.29
The unit for the area is in square cm, or cm^2.
The two area values above are based on pi = 3.14, so they are approximations.
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Explanation:
The radius of the circle is r = 30 because OA = 30.
The full circle has area A = pi*r^2 = 3.14*30^2 = 2826 cm^2 approximately
However, we only want 120/360 = 1/3 of this full area to get the area of the pizza slice. So the area of the pizza slice is approximately (1/3)*2826 = 942 cm^2
This is not the final answer, but helps get us there.
What we just calculated was the approximate area of the entire figure: the yellow area plus the white triangle.
If we can find the area of the white triangle, and subtract it off, then we'll find just the area of the yellow region only.
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The SAS (side angle side) area formula for a triangle is
Area = 0.5*p*q*sin(R)
where p,q are the sides and angle R is between those sides.
Here we have p = q = 30, which are sides OA and OB, and we have R = 120 degrees as the central angle.
So the area of triangle AOB is...
Area = 0.5*p*q*sin(R)
Area = 0.5*30*30*sin(120)
Area = 450*sqrt(3)/2
Area = 225*sqrt(3)
This value is exact.
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The area of the yellow region is therefore
(area of full figure) - (area of triangle)
(942) - (225*sqrt(3))
942 - 225*sqrt(3)
This is approximate because we used pi = 3.14 as an approximation earlier.
You could then use your calculator to say
942 - 225*sqrt(3) = 552.288568
This rounds to 552.29
