The length of a rectangle is 18 cm, the width is 13.4 cm, and the area of a circle is ()

The length of a rectangle is 18 cm, the width is 13.4 cm, and the area of a circle is ()

(18 + 13.4) × 2 = π × 2R, r = 10, s = π R × r = 314

Function range
The range of function y = (1 / 3) ^ (x ^ 2-2x-1) is______

Because x ^ 2-2x-1 = (x-1) ^ 2-2 > = - 2
And y = (1 / 3) ^ x is a decreasing function
So y = (1 / 3) ^ (x ^ 2-2x-1)

arcsin （sin t）=t?

No
The range of arcsinx is [- π / 2, π / 2]
So it's not right
=T + 2K π or 2K π + π - t
It must be reduced to [- π / 2, π / 2]
And sin (arcsint) = t holds

There is a rectangular board, the perimeter is 24 cm, its length and width ratio is 3:5, what is the area of this rectangular board?

Length = 24 ﹣ 2 × 3 ﹣ 3 + 5 = 4.5cm;
Width = 4.5 × 5 △ 3 = 7.5cm;
Area = 4.5 × 7.5 = 33.75 square centimeter
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Answer to question 7 on page 55 of Primary School Mathematics Evaluation Handbook grade 6 Volume 2

The upper limit root X and lower limit X of definite integral of SiNx / X

In this paper, we first discuss the convergence of the definite integral of SiNx / X on the infinite interval, which can be proved to be convergent, because its integral is equal to the value 1 of the low-pass filter with width 1 on the zero frequency. Secondly, SiNx can be expanded into x-x ^ 3 / 3! +. Then the Taylor expansion of SiNx / X can be obtained, and then the above definite integral can be carried out item by item

Grade four summer composition

There is a cylindrical pile, cut along the diameter, the section is a square, the circumference of the bottom of the cylinder is 12.56 cm, calculate the volume of the cylinder?

False feelings and love,
The section cut along the diameter is a square, indicating: diameter = height
The diameter and height are:
12.56 △ 3.14 = 4 (CM)
The volume of the cylinder is (^ 2 is the square)
3.14 × (4 △ 2) ^ 2 × 4 = 50.24 (cm3)

What operation symbol is filled in between four 5S, and the result is equal to 3?

-(（5 + 5） / 5 - 5)

Let z = Z (x, y) be determined by the equation x ∧ 2Z ∧ 3 + 2Y ∧ 2Z ∧ 2-x ∧ 2 + y ∧ 3 = 0

The partial derivative of X on both sides: 2XZ ^ 3 + x ^ 2 * 3Z ^ 2 z'x + 2Y ^ 2 * 2Z * z'x-2x = 0, Z'x = (2x-2xz ^ 3) / (3x ^ 2Z ^ 2 + 4Y ^ 2Z)
The partial derivative of Y on both sides: x ^ 2 * 3Z ^ 2 * z'y + 4yz ^ 2 + 2Y ^ 2 * 2Z * z'y + 3Y ^ 2 = 0, then z'y = - (3Y ^ 2-4yz ^ 2) / (3x ^ 2Z ^ 2 + 4Y ^ 2Z)
dz=Z'xdx+Z'ydy=(2x-2xz^3)/(3x^2z^2+4y^2z)dx-(3y^2-4yz^2)/(3x^2z^2+4y^2z)dy