The effective value of a sinusoidal voltage is 380V, the frequency is 50 Hz, the starting value of timing is equal to 380V, and the expression of its instantaneous value is

The effective value of a sinusoidal voltage is 380V, the frequency is 50 Hz, the starting value of timing is equal to 380V, and the expression of its instantaneous value is

u=380*√2sin（314t+Π/4）
The peak value of sinusoidal voltage is √ 2 times of RMS
When t = 0, u = 380
T = 0.02s is a period, u = 380

What is 3.75 divided by 2.5

1.5

Let a third-order matrix A have an eigenvalue of 1, and the determinant A is equal to 0, and the sum of the main diagonal elements of a is 0, find the other two eigenvalues of a!

The formula A is equal to 0, so 0 is the eigenvalue of A
The sum of all eigenvalues is equal to the sum of all elements on the diagonal of the matrix
So 1 + 0 + a = 0
So the last eigenvalue is - 1

How much is the result of dividing 36 ° 22'52 ″ x2-15 ° 20 'by 4? Give the answer in 15 minutes and 5 minutes

36°22′52〃X2-15°20′÷4
=72°45′44〃-3°50′
=68°55′44〃

How to know the boundedness of sin (x0 + △ x) / 2)
Δ x tends to zero
Isn't SiNx a bounded function

lim(△x->0) sin( x0+△x)/2)
=sin(x0/2)
|SiNx | ≤ 1: bounded
|Sin (x0 + △ x) / 2) | ≤ 1: bounded

Simple calculation of 2.5-2.5 × 0.8

2.5×(1-0.8)=2.5×0.2=0.5

It is known that P (1,2) is a certain point in the circle x ^ 2 + y ^ 2 = 9. If two mutually perpendicular arbitrary chords intersect at points B and C through P, then the trajectory equation of point m in BC is
Note: the answer is x ^ 2 + y ^ 2-x-2y-2 = 0,

Since it is vertical, MP = BM = cm
BM^2+MO^2=R^2=9=MP^2+MO^2
So let m (x, y) have the distance formula
(x-1)^2+(y-2)^2+x^2+y^2=9
After finishing, you can get
2x^2+2y^2-2x-4y=4
Namely: x ^ 2 + y ^ 2-x-2y = 2
(x-1/2)^2+(y-1)^2=13/4
It's also a circle

The yield of oil is 42%. How many kilos of rapeseed are used to extract 2100 kilos of oil

Divide 2100 kg by 42% to get 5000 kg of rapeseed

If the line and hyperbola x2-4y2 = 4 intersect at two points a and B, if the midpoint coordinate of line AB is (8,1), then the equation of the line is______ ．

Let a (x1, Y1), B (X2, Y2), then X1 + x2 = 16, Y1 + y2 = 2, ∵ x12-4y12 = 4, x22-4y22 = 4, ∵ 16 (x1-x2) - 8 (y1-y2) = 0, ∵ KAB = Y1 − y2x1 − x2 = 2, ∵ the equation of straight line is Y-1 = 2 (X-8), that is, 2x-y-15 = 0

Quadratic solution of equation 3x + 5x = 0.9x = (X-2)

The quadratic of 3x + 5x = 0
x(3x+5)=0
x1=0 x2=-5/3
Quadratic of 9x = (X-2)
9x²-（x-2）²=0
（3x+x-2）（3x-x+2）=0
(4x-2)(2x+2)=0
(2x-1)(x+1)=0
x1=1/2 x2=-1
If you don't understand this question, you can ask,