Unit 1 Understanding of Circle
Test center 1: the basic concept of circle? Center, radius and diameter.
Test center 2: Does the center of the circle determine the position of the circle? Radius? Diameter? Determine the size of the circle.
Test site 3: the relationship between radius and diameter.
Test site 4: the relationship between square, rectangle and circle.
1. Draw the largest circle in a square with a side length of 6 cm. The radius of this circle is (). In a picture with a length of 16 cm and a width of 8 cm.
Draw a circle with a diameter of 4 cm on a rectangle. You can draw at most () such circles.
Test site 5: Common axisymmetric figures and their symmetry axes.
Test site 6: the concept and relationship of circumference, pi and diameter (radius) of a circle.
The formula of circumference of test center 7 and its application. (a), tell the diameter? Find the circumference.
Test site 7: Pi formula and its application. 2. What is the radius? Find the circumference.
Test site 7: Pi formula and its application. 3. Tell the outside line? Find the diameter.
Test site 7: Pi formula and its application. (4), tell the circumference? Find the radius.
Test site 8: area formula of circle and its application. (5) tell the radius? Find that area.
The minute hand of the clock is 5 cm long. From 1 to 2 o'clock, the area swept by the minute hand tip is () cm2.
The minute hand of the clock is 5cm long. This clock goes from 12 to 6 o'clock, and the area swept by the minute hand is () cm2.
A: 78.5
b、 19.625 C、 1 17.75 D、47 1
Test site 8: area formula of circle and its application. (2) Talking about diameter: finding the area.
Test site 8: area formula of circle and its application. (3) Tell the surrounding area: find the area
Test center 9: Mixed calculation of circumference, area, diameter and radius of a circle.
1, a log, the circumference of its cross section is 62.8 cm, and its cross-sectional area is how many square centimeters.
Test center 10: the nature, perimeter and area of the semicircle.
1, the formula of the circumference of a semicircle is ()
2. Divide the circle with the circumference of 12.56 cm into two semicircles on average, and the circumference of each semicircle is () cm.
Test center 1 1: knowledge points whose perimeter and area are easily confused.
Judgment: 1, the perimeters of two circles are equal, then the areas of these two circles ().
2. A circle with a radius of 2 cm has the same circumference and area. ( )
3. Two circles with equal areas must also have equal perimeters. ( )
Test center 12: Comparison of perimeter and area.
1, when the perimeter is equal, the area of () is the largest; When the areas are equal, the perimeter of () is the smallest.
2. Square, rectangle and circle with equal perimeters, () has the largest area.
3. Two ants A and B walk around a square with a side length of 2cm and a circle with a diameter of 2cm, respectively, at the same speed. (b) crawl first.
Finish a lap.
Test site 13: expansion (contraction) of the circle.
1. The radius of the circle is enlarged by 2 times, the diameter is enlarged by () times, the circumference is enlarged by () times and the area is enlarged by () times.
2. When the radius of a circle is magnified 5 times, the circumference is magnified (), the area is magnified () times, and the pi is ().
3. The radius of the big circle is 4cm, the diameter of the small circle is 4cm, the circumference of the big circle is () times that of the small circle, and the area of the big circle is small.
() times the area.
4. If the radius of the circle decreases by 1, the area will decrease ().
Test center 14: shaded area.
The common methods to find the shadow area are: (addition and subtraction), (clipping) and equal division.
Test center 15: the area of the circle. Area of a circle = (area of a big circle)-(area of a small circle), and the formula S circle = (π R2-π R2) = {π (R2-R2)}
A circular flower bed with a diameter of 8 meters, and a stone road with a width of 1 meter should be built around the flower bed.
(1) What is the area of the stone road?
(2) If the price per square meter is 100 yuan, how much will it cost to build this stone road?