I'm very interested in Chinese. 3. It rained all day this morning

I'm very interested in Chinese. 3. It rained all day this morning

I sing as I walk
I am very interested in Chinese
It rained heavily all day today

Teacher, you go first

Teacher, you go first
The adverbial should be changed before the verb: teacher, you go first

We came to the campus singing

Singing, not singing

∫∫ (x ^ 2 + y ^ 2) ds, ∑ is the surface of the solid surrounded by z = √ (x ^ 2 + y ^ 2) and z = 1
As shown in the picture

Σ consists of two parts, Σ 1 is the cone and Σ 2 is the plane z = 1
First calculate ∑ 1: the equation is Z = √ (x ^ 2 + y ^ 2)
dz/dx=x/√(x^2+y^2 ),dz/dy=y/√(x^2+y^2 )
dS=√(1+(dz/dx)²+(dz/dy)²)=√2dxdy
∫∫ (x²+y²) dS
=√2∫∫ (x²+y²) dxdy
=√2∫∫ r²*r drdθ
=√2∫[0→2π]dθ∫[0→1] r³ dr
=√2π/2
First calculate ∑ 2: the equation is Z = 1, DS = DXDY
∫∫ (x²+y²) dS
=∫∫ (x²+y²) dxdy
=∫∫ r²*r drdθ
=∫[0→2π]dθ∫[0→1] r³ dr
=π/2
The final result is: √ 2 π / 2 + π / 2 = π / 2 (√ 2 + 1)

Square factorization of (a-b) + 4 (a-b) C + 4C

=(a-b)^2+4(a-b)c+4c^2
=a^2-2ab+b^2+4ac-4bc+4c^2

Is 2 divisible by 8 or 8 divisible by 2

8 is divisible by 2
It can also be said that 2 can divide 8

It is known that F 1 and F 2 are the two focal points of the ellipse x squared / 100 + y squared / 64 = 1, and P is a point on the ellipse. Find the maximum value of Pf1 * PF2
Well, just like the title

It is known that F & # 8321;, F & # 8322; are the two focuses of the ellipse X & # 178 / / 100 + Y & # 178 / / 64 = 1, and P is a point on the ellipse. Find the maximum value of PF & # 8321; &# 8226; PF & # 8322
a=10,b=8,c=6；F₁(-6,0),F₂(6,0).
The elliptic equation is rewritten as a parametric equation: x = 10cost, y = 8sint, t ∈ R. then the coordinates of point P on the ellipse are (10cost, 8sint)
So pf & # 8321; = (- 6-10cost, 8sint); PF & # 8322; = (6-10cost, 8sint);
So pf & # 8321; &# 8226; PF & # 8322; = (- 6-10cost) (6-10cost) + 64sin & # 178; t = - (36-100cos & # 178; t) + 64sin & # 178; t
=100cos²t+64sin²t-36=100cos²t+64(1-cos²t)-36=36cos²t+28≦36+28=64
When t = 0 or π, this value is obtained. When the maximum value is obtained, the coordinates of P are (10,0) or (- 10,0)

A set of prime numbers less than 15

It's 2.3.5.7.11.13
One is neither prime nor sum

Function image symmetry
Who can define the symmetry of function about origin, y = x, X axis and Y axis

Origin g (x) = - f (- x)
y=x g(x)=f^(-1)(x)
X axis g (x) = - f (x)
Y-axis g (x) = f (- x)

If the function y = f (x) defined on R increases monotonically in the interval [0, + ∞), and f (- x) = f (x), then f (2x-1) < f (1 / 3)
The value range of X is ()

∵ f (- x) = f (x) ∵ f (x) is an even function
And ∵ f (x) increases monotonically in the interval [0, + ∞) and decreases monotonically in the interval (- ∞, 0)
To make f (2x-1)