a circle with radius of 9cm sits inside a circle with radius of 11cm. what is the area of the shaded region?
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Answer:
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Explanation:
Method 1
We can use the pythagorean theorem to find x.
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Method 2
Use the sine ratio to find x. You'll need a reference sheet or the unit circle, or simply memorize that sin(60) = sqrt(3)/2
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Method 3
Similar to the previous method, but we'll use tangent this time.
Use a reference sheet, unit circle, or memorize that tan(60) = sqrt(3)
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Method 4
This is a 30-60-90 triangle. In other words, the angles are 30 degrees, 60 degrees, and 90 degrees.
Because of this special type of triangle, we know that the long leg is exactly sqrt(3) times that of the short leg.
The short leg is always opposite the smallest angle (30 degrees).