It is known that the effective value of a sinusoidal alternating current electromotive force is 220 V, the frequency is 50 Hz, and the initial phase is 30 degrees

It is known that the effective value of a sinusoidal alternating current electromotive force is 220 V, the frequency is 50 Hz, and the initial phase is 30 degrees

AC maximum EM = 1.414 * 220 * sin (ω T + 30 °)
Period T = 1 / 50
Angular frequency ω = 2 * 3.14 * 50
Instantaneous value 1.414 * 220 * sin (ω T + 30 °)

What is the difference between 220 V AC 50 Hz and 60 Hz

The frequency is different. This difference is obvious in transformer and motor
The efficiency and reliability of the transformer with rated frequency of 50 Hz will decrease when it is used at 60 Hz. The motor with rated frequency of 50 Hz will cause premature aging when it is used at 60 Hz

The requirement of computer power supply is 220 V 50 Hz DC power supply 220 V 100 Hz DC power supply 220 V 50 Hz AC power supply 220 V 100 Hz AC power supply

220 V 50 Hz AC power supply

Find the greatest common factor of 30 and 45 by short division

So the greatest common factor of 30 and 45 is 3 × 5 = 15

Given 3A + B + 6 = 24, find the value of 6A + 2b-6

According to the known conditions, 3A + B = 18
So 6A + 2b-6 = 2 (3a + b) - 6 = 30

Given the line segments a, B and C, draw a line segment AB so that ab = a + 2b-c (draw with ruler)

First, draw a long line with a ruler, and set the left end point as a,
1. Use a compass to check the length of line segment a, and draw to the right with point a as the starting point, so that the other end point is C;
2. Use a compass to check the length of line segment B, and draw to the right with point C as the starting point, so that the other end point is d;
3. Use a compass to check the length of line segment B, draw to the right with point D as the starting point, and the other end point is e;
4. Use a compass to check the length of line segment C, and draw to the left with point E as the starting point, so that the other end point is B;
That is line ab

For any a belonging to - 4 to 5, the square of inequality x minus 6x is less than a (X-2), and the value range of X is constant

X & # 178; - 6x0 for a belongs to [- 4,5],
Key: A as a variable, X as a parameter; a function, the endpoint can be established;
If a = - 4 is substituted by: - X & # 178; + 2x + 8 > 0, then: - 2 is obtained

The area of an isosceles right triangle ABC is 35 square centimeters. What is the area of a semicircle?

The area of an isosceles right triangle ABC is 35 square centimeters. What is the area of a semicircle?
The right side of isosceles right triangle ABC is l, and the radius of circle is r
S=L^2/2=35
L^2=70
L=70^0.5
L^2=R^2+R^2
2*R^2=L^2=70
R^2=35
R = 35 ^ 0.5cm
Area of semicircle s semicircle = pi * R ^ 2 / 2 = 35 * pi / 2 square centimeter

Several high school quadratic functions
Please write down the process, I have all the answers, I just want to weigh (idea)
1. Given the quadratic function y = ax & sup2; + BX + C and the first function y = K (x-1) - K & sup2 / 4, if their images have only one common point for any real number k, then the analytic expression of the quadratic function is________ .
2. If the maximum value of function y = - X & sup2; - 2aX (0 ≤ x ≤ 1) is a & sup2;, then the value range of real number a is ()
A.0≤a≤1 B.0≤a≤2 C.-2≤a≤0 D.-1≤a≤0
3. If the function f (x) = ax & sup2; + 2aX + 1 has the maximum value 4 on [- 3,2], then the value of a is_________ .
4. If for any k on [- 1,1], the minimum value of function f (x) = x & sup2; + (K-4) x-2k + 4 is a positive number, find the value of X
5. If f (x) = x & sup2; + (a + 2) x + 3, where the image of X on [a, b] (a < b) is symmetric with respect to the line x = 1
(1) Find a, B
(2) Find the maximum and minimum of function f (x) in the interval [a, b]

1. It can be seen from the question that a ≠ 0, K ≠ 0, so that y = ax & sup2; + BX + C = K (x-1) - K & sup2; / 4, sort them into quadratic function form, write the expression of Δ, so that their image has only one common point for any real number k, as long as the coefficients of K & sup2;, K are all 0, you can try 2

How to calculate the partial derivative of Y, where the last y is the exponent z = (1 + XY) y
The last y is the exponent, which requires a partial derivative of Y,

z=e^[ln(1+xy)^y]
=e^[yln(1+xy)]
z'=e^[yln(1+xy)]*[ln(1+xy)+y*1/(1+xy)*x]dy
=e^[yln(1+xy)][ln(1+xy)+xy/(1+xy)]dy