The circumference of a circle is 12.84 cm longer than its diameter. What is the area of the circle?

The circumference of a circle is 12.84 cm longer than its diameter. What is the area of the circle?

3.14d-d=12.84
d=6,r=3
3.14*3*3=28.26

As shown in the figure, the bottom side of the hexagonal prism is 5cm long and the side edge is 4cm long. Observe the model and answer the question
1. How many faces are there? What are their shapes? Which faces have the same shape and area?
2. How many edges are there? What are their lengths?
I don't have a picture. The picture is a hexagonal prism. It's a horizontal hexagonal prism. If any expert can answer it, I really appreciate it!)

(1) There are 8 faces in total, the bottom is a regular hexagon, the side is a rectangle, the shape and area of the upper and lower bottom are exactly the same, and the shape and area of the side are exactly the same
(2) There are 18 edges, including 6 lateral edges and 4 lateral edges. The length of the bottom side is 5cm

If P (x, y) satisfies (x-4cos θ) 2 + (y-4sin θ) 2 = 4 (θ∈ R), then the area of the region where p (x, y) is located is ()
A. 36πB. 32πC. 20πD. 16π

∵ point P (x, y) satisfies (x-4cos θ) 2 + (y-4sin θ) 2 = 4 (θ∈ R). Point P is a point on a circle with (4cos θ, 4sin θ) as the center and 2 as the radius. As shown in the figure, the area where point P (x, y) is located is the shadow part of the figure, which is a ring, the radius of the outer ring is 6, and the radius of the inner ring is 2

As shown in the figure, the power supply voltage remains unchanged, R1 = 6 Ω, R2 = 4 Ω. When the switches S1, S2 and S3 are closed, the number of current A1 is 1a, and the number of ammeter A is 2.5A
1. Resistance value of resistance R3 and indication of voltmeter
2. When switches S1 and S2 are disconnected, the number of ammeter A1. A and voltmeter V will be displayed
chart

1、 At this time, the current through R1 is I '= 1a, the current through R3 is I' '= I-I' = 2.5a-1a = 1.5A. The voltage provided by the power supply is u = i'r1 = 1a × 6 Ω = 6V. The resistance value of R3 is R3 = u / I '' = 6V / 1.5A = 4 Ω

Explain the function of dashes in the following sentences
1. Lost the battle, enlisted and issued the various orders of the headquarters. I did not stop, but thought in my heart, "what's the matter again?"
He said that French language is the most beautiful language in the world - the most clear and accurate
"My friends," he said, "I -- I --"
Then he stayed there, his head against the wall, without saying a word, just made a sign to us: "school is over - you go."

1 turning point
The extension of discourse
A pause in tone

The length of the line L intersecting the ellipse at two points AB that passes through the left focus F1 of the ellipse x ^ 2 / 5 + y ^ 2 = 1 and has an inclination angle of 45 °

Left focus F1 (- 2,0) of ellipse x ^ 2 / 5 + y ^ 2 = 1
The inclination angle is 45 and the slope is 1
therefore
The equation of line L is y = x + 2
We can get the equation
x²+5x²+20x+20=5
6x²+20x+15=0
x1+x2=-10/3
x1x2=5/2
y1+y2=2/3
y1y2=x1x2+2(x1+x2)+4
=5/2+2*(-10/3)+4
=-1/6
The length of the string is
√[(x1-x2)²+(y1-y2)²]
=√[(x1+x2)²-4x1x2+(y1+y2)²-4y1y2]
=√[100/9-10+4/9+2/3]
=√[20/9]
=2√5/3

The circumference of a rectangle is 24 cm, the length is 5 / 7 of the width, and the area of the rectangle is

24 / 2 = 12 12 * 5 / 5 + 7 = 5 12-5 = 7 5 * 7 = 35, with an area of 35

Known π

sin（π-α）+cos（π+α）=1/5
sin α -cosα =1/5
sin α =1/5 + cosα
∵π

Given the quadratic equation of one variable 8x2 - (2m + 1) x + M-7 = 0, the values of M are obtained according to the following conditions: (1) two reciprocal numbers; (2) two opposite numbers; (3) one is zero; (4) one is 1

Let two of the original equations be reciprocal of X1 and X2 (1) ∵ two of them are reciprocal of each other, the product of them is 1x1 · x2 = m − 78 = 1, and the solution is m = 15, (2) ∵ two of them are opposite to each other, ∵ X1 + X2 = 2m + 18 = 0, ∵ M = - 12, (3) when one of them is zero, ∵ M-7 = 0, ∵ M = 7, (4) when one of them is 1, ∵ 8-2m-1 + M-7 = 0, and the solution is m = 0

If y = a ＾ x + B-1 (a > 0 and a is not equal to 1)
If the image passes through the second, third and fourth quadrants, there must be （）
(A) 01 and b > 0
(C)0

c. First, when a ＾ X.A > 1, the function increases monotonically on R, the function crosses (0.1) point, and the function value is greater than zero
0