As shown in the figure, in △ ABC, ad ⊥ BC is at point D, de ⊥ AB is at point E, DF ⊥ AC is at point F. try to explain AE: ab = AF: AC

As shown in the figure, in △ ABC, ad ⊥ BC is at point D, de ⊥ AB is at point E, DF ⊥ AC is at point F. try to explain AE: ab = AF: AC

So angle bed = angle AED = 90 degrees, because DF is perpendicular to F, so angle AFD = 90 degrees, so angle AED + angle AFD = 180 degrees, so a.e.d.f four points are in a circle, so angle AFE = angle ade, because ad is perpendicular to D, so angle ADB = angle ade + angle BDE = 90 degrees, because angle bed = angle B + angle BDE = 90 degrees, so angle B + angle BDE = angle BDE + angle ade = 90 degrees

The remainder of y = x ^ 3-2x ^ 2 + ax + B divided by (x-1) (x + 1) is 0 to find the value of a and B
This kind of problem is not big,
Sorry, I have the wrong number! Is (X-2) (x + 1)

Note that in the expression of Y, X has a cubic term, the coefficient is 1, the constant term is B, and (x-1) (x + 1) = x ^ 2 - 1, X has the highest quadratic term, the coefficient is 1, the constant term is - 1, so y is divided by (x-1) (x + 1), and the quotient should be (X-B), so (x ^ 2 - 1) (x - b) = x ^ 3 - BX ^ 2 - x + B = x ^ 3 - 2x ^ 2 + ax +

A is the smallest positive integer, B is the opposite of the largest negative integer, and it is the number represented by the point with the smallest distance from the number axis to the origin
A is the smallest positive integer, B is the opposite of the largest negative integer, and it is the number represented by the point with the smallest distance from the number axis to the origin

a=1,b=1,c=0,3

If - 2xym and 13xny3 are similar, then ()
A. m=1，n=1B. m=1，n=3C. m=3，n=1D. m=3，n=3

∵ - 2xym and 13xny3 are of the same kind, so C

220 V heating pipe connected to 380 V power supply
If you don't want to use the zero line, can you connect six 220 V heating tubes in series and then connect them at corners? Is each heating tube 190 v. how to calculate the current? If you use the zero line and connect them in parallel, how thick is the zero line, and how much is the current? Is it OK if you don't connect the zero line?

The current of heating tube can be obtained by Ohm's law U / R after calculating the resistance of heating tube according to the power of heating tube r = u & # / P
If the parameters of the heating tube are the same, there is no current on the zero line, so that it is possible to not connect the zero line after the star connection

1/2x²y,2/3x²,3/4xy²
1/xy,2/x²y+xy²
x/x²-4,2/（x+2）²

The common denominator of the first group is 12x & # 178; Y & # 178;
Therefore, they are: 6y / (12x & # 178; Y & # 178;), 8y & # 178; / (12x & # 178; Y & # 178;), 9x / (12x & # 178; Y & # 178;)
The common denominator of the second group is XY (x + y)
So, the order is: (x + y) / [XY (x + y)], 2 / [XY (x + y)]
The common denominator of the third group is (X-2) (x + 2) & #;
Therefore, the order is: X (x + 2) / [(X-2) (x + 2) & # 178;], 2 (X-2) / [(X-2) (x + 2) & # 178;]

In a resistance circuit, connect a capacitor in series, know that the voltage is 220 V, the resistance is 200 Ω, the capacitance is 2uF, and calculate the voltage at both ends of the resistance
It's alternating current
50 Hz

This calculation involves complex number (phasor method), z = R + 1 / J ω C resistance voltage ur = 220 * (R / | Z |), | Z | = √ (R & # 178; + (1 / ω C) & # 178;) = 1669, so voltage ur = 220 * 500 / 1669 = 65.9, this is the content of University circuit analysis, if you are interested, please see the fifth edition of circuit

A math problem is as follows: (do it with general score. Write the process clearly. Be correct)
The land area of Asia accounts for about 1 / 3 of the global area. The land area of Africa and South America accounts for about 1 / 5 and 3 / 25 of the global land area respectively?
The denominator should be the same.

Is this a practical problem~
If not
Asia = 1 / 3 = 25 / 75
Africa = 1 / 5 = 15 / 75
South America = 3 / 25 = 9 / 75
If so, we should also consider the ratio of global land area to water surface~
It's like water: Land = 7:3
Asia = 1 / 3 = 250 / 750
Africa = 1 / 5 * 7 / 10 = 105 / 750
South America = 3 / 25 * 7 / 10 = 63 / 750
In any case, the conclusion is the same: Asia is the largest and South America the smallest~

My battery is 12 V, 80 a! How much voltage and current should I charge it

11 ~ 12V charging voltage
Charging up to 50 a

As shown in the picture, there is a mural, the highest point a is 4m above the ground, and the lowest point B is 2m above the ground. If you view it from the place C, which is 1.5m above the ground, the viewing angle θ is the largest when it is far from the wall

Let CD = XM, let CD = XM, then θ = {ACD \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\inthis case, the angle of view is the largest (16 points)