Cut a cylinder with a circumference of 12.56 square centimeters and a height of 5 centimeters along the diameter of the bottom. How many square centimeters will the surface area increase

Cut a cylinder with a circumference of 12.56 square centimeters and a height of 5 centimeters along the diameter of the bottom. How many square centimeters will the surface area increase

D = C divided by 3.14 = 4 (CM), s = 4 times 5 = 20 (CM), 20 times 2 = 40 (CM)

Cos 45 °, ﹥ 8226; Tan 45 ° + radical 3.tan 30 ° - 2cos 60 °, ﹥ 8226; sin 45 °

Original form
=cos45°×(sin45°/cos45°)+ √3×√3/3-2×1/2×sin45°
=sin45°+1-sin45°
=1

Partial derivative ln (XY)
Partial derivative u = ln (XY)
For: on U (x), u (y) of the partial derivative, the best detailed point
I know u = ln (x) = 1 / X

Because: u = ln (XY)
du=1/(xy)*[ydx+xdy]
du=dx/x+dy/y;
So:
u(x)=1/x ;
u(y)=1/y .

All formulas of grade 9 in Chemistry (literal expressions and chemical equations)

Chemical equation reaction phenomenon 2mg + O2 is used to ignite 2mg O and burn violently. Bright white light is produced to produce white solid and release heat. A large amount of white smoke is produced. The red metal of fireworks 2Cu + O2 Δ 2CuO turns into black solid

Add, subtract, multiply and divide 7, 8, 5, 3 into 24

1: (7 × (8 - 5)) + 32: 7 × (8 - 5) + 33: 7 × 5 -(8 + 3)4: (7 × 5) - (8 + 3)5: 7 × 5 - 8 - 36: (7 × 5) - 8 - 37: (7 × 5 - 8) - 38: ((7 × 5) - 8) - 39: 7 × 5 -(3 + 8)10: (7 × 5) - (3...

It is known that two first-order functions Y1 = 3x-4, = 3-x if Y1

3x-4

The perimeter of a round flower bed is 31.4 meters. How many square meters does it cover?

2, = 3.14 × 52, = 3.14 × 25, = 78.5 square meters. A: this flower bed covers an area of 78.5 square meters

1,5,5,5 and 1,7,7,7 are 24 points. Who will?
Today, I was asked this question, but I really can't figure it out

（5-1÷5）×5=24
Second, there is no way

Let KX + (K + 1) y = 2 √ 505 (k is a positive integer) and the area of the figure enclosed by two coordinate axes be sk,
S1+S2+S3+… +S2019=?

Sk=1/2 (2√505 / k) (2√505 / (k+1) )=1010/( k(k+1) )S1+S2+S3+… +S2019=1010( 1/1·1/2+1/2·1/3+… +1/2019·1/2020 )=1010( (1/1-1/2)+(1/2-1/3)+… +(1/2019-1/2020) )=1010(1-1/2020)=2019/2

Who can tell me about the density conversion problem in the conversion formula between the quantity concentration and the mass fraction of a substance

Derivation:
M1 is the mass of solute, M is the molar mass of solute, the amount of solute in solution N = M1 / M; M2 is the mass of solution, ρ is the density of solution, v = m2 / ρ. But in chemistry, the unit of mass is generally gram, and the unit of density is gram / cm3, so the unit of volume is cm3, and the unit of mass concentration is mole / L, which is converted into liter, so it is divided by 1000
Mass concentration C = n / v = (M1 / M) / [(m2 / ρ) / 1000]
The mass fraction is expressed by P%, P% = M1 / m2,
The conversion formula between the mass concentration and the mass percentage concentration of the substance is
c=1000ρP%/M