Math Problems About Circles in Middle School Mathematics in junior high school, about circles

1.First draw 2 diameters perpendicular to each other, 2Find the midpoint of the 4 radii determined by the diameter of the 2 strips.

3.Draw a circle with 4 midpoints as the center of the circle and the radius of the circle as the radius, and the 4 circles obtained are the findings.

The maximum diameter is:

50/2=25(cm)

The four circles are tangent to each other and tangent to the great circle, satisfying the theme.

Let the diameter of the circle be d and the radius will be r d=50

Then r+r+(d 2+d 2) 1 2=d, i.e., d+root, 2 times, d=50

This results in d=50 (root number 2-1) = 50*

r+r+(d 2+d 2) 1 2=d represents r+r+root (d + d).

I wanted to draw it, but I couldn't draw it, so I hope I can understand it.

The four circles are tangent to each other, and all are inscribed with the great circle, let the radius of the small circle be r from the center of the big circle to the center of the small circle is r 2 times the root number (it can be seen by connecting the four circles to form a square) r + r 2 times the root number is equal to 25, then r is.

25 (root numbers 2-1).

Done: Thank you.

According to the upstairs, the four circles coincide, how can you cut it, less raw materials.

Question 11 has a detailed diagram and process.

4 roots No. 2 cm. The perpendicular line of the string is bisected by the perpendicular diameter theorem. If the diameter length is 6, the radius of the excavation length is 3

Connects the center of the circle to the end of the chord. The diameter of the chord is 1 and 5, so 3-1 = 2 and the chord centroid distance is 1According to the Pythagorean theorem, half of the string is 2 number 2, and the chord length is 4 number circles, and the quadrilateral triangles are complementary, so the ratio of the four inner angles is:

20*8=160°3.Make de perpendicular to ab. Because od is perpendicular to d, ad=cd=2, and the loss is because ab=5, so ao=ob=,do=2,ed=,eo=,db=,db=root number 134

No figures. The level is limited, please forgive me if there is any error.

Area = 1 4 circle = 1 4 r square = 16 , r = 8 sector closed circumference = 1 4 circle circumference = 1 4 * 2 r = 4 is also the perimeter of the area at the bottom of the cone.

2 r1=4 , the radius of the grinding cone r1=2

The hypotenuse is 8 heights, blind and stupid = root number (8 square - 2 square) = 2 root number 15

Let the radius of the circle be r, the radius of the bottom surface of the cone be r, and the height of the cone be h: 90° 360° r = 16

r=8The length of the arc is: 90° 360° 2 8=4 The length of the arc is the circumference of the bottom surface of the cone.

2πr=4π

r = 2 conical sock wisdom bucket chain bus length is the radius of the arc r = 8 according to the Pythagorean theorem: h pin answer = r -r = 60h = 2 15

If the modification is unsuccessful, let's look at the picture yourself.

1. This is an intersecting string theorem, and there is no need to prove it. 2. It should be "let the midpoint of BC be E, connect EP and extend the intersection of AD to F, and verify EF AD".

Proof that E is the midpoint of BC, triangle BCP is RT triangle, PE=BC2, CE=BE=PE, and in RT triangle ADP, pad=dpf, EF AD.