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U = f (x + y + Z, X & # 178; + Y & # 178; + Z & # 178;) for Du sum & # 8706; &# 178; U / &# 8706; X & # 178; Content such as the title, how to calculate, I worked out a long string. Feel wrong
The current calculation formula of three-phase motor I = P / 1.732/u/cos Φ, what is cos Φ and why there is a cos Φ
Is the formula I = P / 1.732/u right or wrong? Under what circumstances will cos Φ be used
The formula I = P / 1.732/u is wrong, and the correct one is I = P / (1.732 * u * cos Φ)
Cos Φ is the cosine of the phase difference (Φ) between voltage and current in AC circuit, which is called power factor. It is expressed by the symbol cos Φ. In numerical value, power factor is the ratio of active power and apparent power, namely cos Φ = P / s
The power factor is related to the load nature of the circuit. For example, the power factor of the resistance load such as incandescent bulb and resistance furnace is 1. Generally, the power factor of the circuit with inductive or capacitive load is less than 1. The power factor is an important technical data of the power system. The power factor is a factor to measure the efficiency of electrical equipment, It shows that the reactive power of the circuit used for alternating magnetic field conversion is large, which reduces the utilization rate of the equipment and increases the loss of line power supply. Therefore, the power supply department has certain standard requirements for the power factor of the power consumption unit
Solving inequality loga (x-4) - log (2x-1) > 0 (a > 0 and a ≠ 1)
loga(x-4)-log(2x-1)>0
That is, loga (x-4) > log (2x-1)
(1) a>1
Then x-4 > 2x-1 > 0
∴ x1/2
There is no solution
(2) 0
As shown in Figure 1, in RT △ ACB, ∠ ACB = 90 °, AC = 3, BC = 4, the moving circle O passing through point C and the hypotenuse AB are tangent to the moving point P, connecting CP
(1) When the circle O is tangent to the right angle side AC, as shown in Figure 2, calculate the length of the radius r of the circle O. (2) the length of the chord CP will change with the position of the tangent point P, and try to find out the value range of the length of the chord CP. (3) when the tangent point P is where, the radius r of the circle O has the maximum value? Try to find out the maximum value
(1) AB = 5, AC and AP are all round, and the center of the circle is on BC, AP = AC = 3, Pb = 2,
PQ ⊥ BC is better than Q, PQ / Pb = Bq / BC = AC / AB = 3 / 5, PQ = 6 / 5, BQ = 8 / 5,
∴CQ=BC-BQ=12/5,∴PC=√(PQ^2+CQ^2)=6√5/5,
If O is used as or ⊥ PC to R, Cr = 1 / 2pc = 3 √ 5 / 5,
OC / Cr = PC / CQ, OC = 3 / 2, that is, r = 3 / 2
(2) the shortest PC is the height of AB: 12 / 5, the largest PC = BC = 4,
∴12/5≤PC≤4
(3) when P and B coincide, the circle is the largest,
Through o as OD ⊥ BC in D, from BD = 1 / 2BC = 2,
∵ AB is the tangent, ∵ ABO = 90 °,
∴∠ABD+∠OBD=∠BOD+∠OBD=90°,∴∠ABC=∠BOD,
∴BD/OB=sin∠BOD=sin∠ABC=BC/AB=4/5,
∴OB=5/2.
The maximum radius is 5 / 2
If the complex z = (A-I) (2 + I) is a real number, then the value of the real number a
Z = 2A + (A-2) I + I Λ 2. Because Z is a real number, A-2 = 0. A = 2
Let C1: x ^ 2 + y ^ 2-10x-6y + 32 = 0, and C2: x ^ 2 + y ^ 2-2ax-2 (8-A) y + 4A + 12 = 0
Point P is a point on the ellipse x2 / 4 + y2 = 1, passing through point P is a tangent of circle C1, the tangent is T1, passing through point P is a tangent of circle C2, the tangent is T2, Q: is there a point P, so that infinitely many circles C2 satisfy pt1 = pT2?
C2:(x-a)^2+(y-8+a)^2=2a^2-20a+52
OP^2=(PT2)^2+(R2)^2
To make pT1 = pt2
Because pT1 is a fixed value
PT2 = sqrt ((XP-A) ^ 2 + (yp-8 + a) ^ 2 - (2a ^ 2-20a + 52)) must be independent of A
(xP-a)^2+(yP-8+a)^2=(2a^2-20a+52)
xP^2-2a*xP+(yP-8)^2+2a(yP-8)=52-20a
[1] 2 * xp-2 * YP = 20 (equal coefficients)
[2] xP^2+(yP-8)^2=52
[3] xP^2/4+yP^2=1
We can get the point P (XP, YP), and then we need to calculate pT1 to prove pT1 = pT2
The rest of the building owners themselves, I sleep
∫ (x ^ 2) * (e ^ 2x) DX for indefinite integral
Step by step integral ∫ (x ^ 2 e ^ 2x) DX = 1 / 2 ∫ x ^ 2 d e ^ 2x) = 1 / 2x ^ 2E ^ 2x-1 / 2 ∫ 2xe ^ 2xdx = 1 / 2x ^ 2E ^ 2x - ∫ Xe ^ 2xdx = 1 / 2x ^ 2E ^ 2x-1 / 2 ∫ xde ^ 2x = 1 / 2x ^ 2E ^ 2x-1 / 2xe ^ 2x + 1 / 2 ∫ e ^ 2xdx = 1 / 2x ^ 2e-1 / 2xe ^ 2x + 1 / 4E ^ 2x + C
English translation
(not too high level, junior high school level is OK)
Today is August 15 of the lunar calendar, the Mid Autumn Festival. Unfortunately, because of the weather, we can't see the big and round moon. But our family still got together and ate tangyuan. It's very sweet. We also ate a lot of delicious moon cakes. We chatted about the Mid Autumn Festival and remembered the Happy Mid Autumn Festival last year
Today is Chinese August 15th,Mid-autumn Festival.But what a pity!Because of the weather reason,we cannot see the big and round moon.But my family went together and eat some big Tangyuan.It is very swe...
Mathematical problems (arithmetic solution)
When a arrives at B, B is 48 meters away from B, and C is 70 meters away from B. when B arrives at B, C is 28 meters away from B. how many meters is the distance between AB and B?
When B walks 48 meters, C walks 70-28 = 42 (meters), which indicates that B's speed is 48 / 42 = 8 / 7 times of C's, and the distance b walks more than C is always 1-1 / (8 / 7) = 1 / 8 of B's distance. B walks 28 meters more than C when it arrives, so AB distance is 28 / (1 / 8) = 224 meters
How to write the area formula of rectangle in letters?
Let the length of a rectangle be a, the width be B, and the area be s,
S=ab
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