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As shown in the figure, the diameter ab of ⊙ o is perpendicular to the chord CD, and the plumb foot is e. if ﹤ cod = 120 ° and OE = 3 cm, then OD=______ Centimeter
The diameter ab of O is perpendicular to the chord CD,
arc BC = arc BD, ﹤ BOC = ∠ BOD = 60 °
And ∵ cos ∵ DOB = OE
OD，
∴OD=3
Cos 60 ° = 6 (CM)
When the radius of a circle is increased to three times of its original size, its circumference will be expanded to () times of its original size, and its area will be expanded to () times of its original size
The perimeter is expanded by 3 times and the area is expanded by 9 times
If the radius of a circle is increased by three times, its circumference will be enlarged by () times, and its area will be expanded by () times If the radius of a circle is enlarged by three times, its circumference will be enlarged by () times and its area will be expanded by () times
The perimeter is 3 times larger and the area is 9 times larger
If the radius of a circle is 2 cm, its perimeter and area are equal
A circle with a radius of 2 cm has a circumference equal to its area
All 12.56
The diameter of a circle is 8 cm. What is the circumference and area of the circle?
14 × 8 = 25.12 (CM),
3.14×（8÷2）2，
=3.14×16，
=24 (square centimeter),
A: the circumference of the circle is 25.12 cm and the area is 50.24 cm 2
The diameter of a circle is 8 cm. How many centimeters is its circumference? How many square centimeters is its area
The circumference is 3.14 × 8 = 25.12 cm
The radius is 8 ￣ 2 = 4 cm
The area is 3.14 × 4 × 4 = 50.24 square centimeter
The diameter of a circle increases from 4cm to 8cm, the circumference increases by () cm, and the area increases by () square centimeter
The diameter of a circle increases from 4cm to 8cm, the circumference increases by (4 π) cm, and the area increases by (12 π) cm2
If the diameter is 8 cm, calculate the radius, perimeter, and area π, take 3.1
radius
8 △ 2 = 4 (CM)
Perimeter
8 × 3.1 = 24.8 (CM)
the measure of area
4 2 × 3.1 = 49.6 (square centimeter)
A circle is 6 cm in diameter and has a circumference______ Cm, area______ Centimeter
14 × 6 = 18.84 (CM)
3.14×（6÷2）2
=3.14×9，
=28.26 (square centimeter)
A: the circumference of the circle is 18.84 cm and the area is 28.26 cm 2
So the answer is: 18.84; 28.26 square
If the diameter of a circle increases from 2 cm to 3 cm, then its circumference increases by ()%, and its area is ()%? Help me ~ ~ ~ (>)_ How to calculate it? Process???
The perimeter is increased by 50%, and the area is 225% of the original
RELATED INFORMATIONS
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- 2. As shown in the figure, O is a point on the diagonal of the square ABCD. The circle with o as the center and OA length as the radius is tangent to m and AB, and ad intersects EF respectively (2) If the side length of the square is 1, find the o radius of the circle
- 3. In the rectangular coordinate system, given the points a 5 to 2 and B 2 to 5, we can make a circle with point a as the center and ab as the radius, and judge the position relationship between the circle a and the X, Y axes
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- 11. As shown in the figure, △ ABC, ab = AC, e is a point on AB, f is a point on AC extension line, and be = CF, if EF and BC intersect at D, prove: de = DF
- 12. As shown in the figure, ad is the angular bisector of △ ABC, de ⊥ AB, DF ⊥ AC, and the perpendicular feet are e and f respectively. If AB = 5, AC = 3, and the area of △ ABC is 16, find the length of de?
- 13. As shown in the figure, given that D is a point on the extension line of edge BC of △ ABC, DF ⊥ AB is at point F, intersects AC at point E, ∠ a = 40 ° and ∠ d = 30 °, then the degree of ∠ ACB is obtained______ Degree
- 14. As shown in the figure, a is a point outside the circle O with radius 1, OA = 2, AB is the tangent line of ⊙ o, B is the tangent point, the chord BC ∥ OA, connecting AC, then the area of the shadow part is equal to () A. Three Four B. π Six C. π 6+ Three Eight D. π 4− Three Eight
- 15. AB is the diameter of ⊙ o, CD, CB are the tangent lines of ⊙ o, B and D are tangent points, connecting OC to ⊙ o to e, straight line AE to BC, BD to F, G. verification: AF bisection ⊙ bad
- 16. As shown in the figure, circle O and circle 1 intersect at points a and B, AC is the diameter of circle O, and the extension lines of Ca and CB intersect circle O1 at points D and E, AC = 12, be = 30, BC = ad, Find ∠ C and de
- 17. It is known that AB and CD are the two diameters of ⊙ o, and the chord CE ∥ ab. it is proved that ad = AE
- 18. As shown in the figure, given that the radius of ⊙ o is 1, AB and ⊙ o are tangent to point a, OB and ⊙ o intersect at point C, CD ⊥ OA, and the perpendicular foot is D, then the value of cos ⊥ AOB is equal to () A. OD B. OA C. CD D. AB
- 19. As shown in the figure, in ⊙ o, D and E are points on the radius OA and ob respectively, and ad = be. Point C is a point on arc AB, connecting CD, CE, Co, ∠ AOC = ∠ BOC Confirmation: CD = CE
- 20. As shown in the figure, BD is the diameter of ⊙ o, point a is the midpoint of arc BC, ad intersects BC at point E, AE = 2, ed = 4 (1) The results were as follows: △ Abe ∽ abd; (2) Find the value of Tan ∠ ADB; (3) Extend BC to f and connect FD so that the area of △ BDF is equal to 8 3. Find the degree of ∠ EDF