Circle


1. Characterize the circle and its parts:

  • circle
  • circular sector
  • circular segment
  • annulus
Solution: 

circle-1-r

2. The distance between the centers of two externally tangent circles is 12 cm, and the sum of the areas of both circles is 80π cm2.

Determine the radii of these circles.
Solution:

kruh2

The radii of the circles are r1 = 8 cm, r2 = 4 cm.

3. Divide a circle with radius R = 28 cm by a concentric circle so that the areas of the resulting parts are equal.

Calculate the radius r of the smaller concentric circle.
Solution:

kruh3

The radius of the smaller concentric circle is r = 19.8 cm.

4. Calculate the radius of a circle if its chord length is t = 16 cm and the height of the corresponding circular segment is v = 5 cm.

Also calculate the area of the segment.
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5. A circle with radius R is divided by a concentric circle with radius r. The ratio of the area of the inner circle to the area of the annulus is the same as the ratio of the area of the annulus to the area of the outer circle.

Determine the radius r.
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6. Three identical circles (r = 8 cm) touch each other.

Determine the area of the region lying between the circles.
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7. An isosceles triangle has a = 10 cm, b = c = 13 cm. A circle is inscribed in the triangle.

Determine what percentage of the triangle's area is occupied by the circle.
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8. The height of the circular segment is 2 cm, and the central angle α = 60°.

Calculate its area S and arc length o.
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9. There is a path 40 cm wide around a circular flowerbed. The flowerbed has a diameter of 3 m 20 cm.

Calculate the area of the path.
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10. The first gear of a gear train has 60 teeth. The second gear meshing with the first has 42 teeth. The third gear meshing with the second has 15 teeth. The first gear rotates seven times.

How many times does the third gear rotate?
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