If A1 = 1, then S4 = () A. 7B. 8C. 15D. 16

If A1 = 1, then S4 = () A. 7B. 8C. 15D. 16

∵ 4A1, 2A2, A3 are arithmetic sequences ∵ 4A1 + A32 = & nbsp; 2A2, ∵ 4A1 + A1 · q22 = 2a1q, that is, 4 + q22 = 2 & nbsp; Q ∵ q = 2 ∵ S4 = A1 (1 − Q4) 1 − q = 1 × (1 − 24) 1 − 2 = 15, so select C
Calculation of electric power and thermal power of motor
When a motor works normally, the voltage is 220 V, the current is 10 A, and the resistance of coil and wire is 3 Ω. Question: what is the electric power, thermal power and mechanical efficiency of the motor?
Electric power = voltage × current = 220V × 10A = 2200W
Thermal power = square of current × resistance = 10 × 10 × 3 = 300W
Thermal power = - 2200.4) / mechanical power = - 300
1. Let the length of BC side in triangle ABC be x (CM), the height ad on BC be y (CM), and the area of triangle be constant. The function image of Y with respect to X is known to pass through points (3,4)
1. Find the analytic function of Y with respect to X and the area of triangle
2. Draw the function image, and use the image to find when 2
1.y=12/x s=6
2. The inverse proportion function is in the first quadrant
It seems that these questions are not too difficult
1. Let the length of BC side in triangle ABC be x (CM), the height ad on BC be y (CM), and the area of triangle be constant. The function image of Y with respect to X is known to pass through points (3,4).
1. Find the analytic function of Y with respect to X and the area of triangle
2. Draw the function image, and use the image to find when 2
If A1 = 1, then S4 = ()
A. 7B. 8C. 15D. 16
∵ 4A1, 2A2, A3 are arithmetic sequences ∵ 4A1 + A32 = & nbsp; 2A2, ∵ 4A1 + A1 · q22 = 2a1q, that is, 4 + q22 = 2 & nbsp; Q ∵ q = 2 ∵ S4 = A1 (1 − Q4) 1 − q = 1 × (1 − 24) 1 − 2 = 15, so select C
What is the thermal power consumed on the resistance of motor coil
1. The thermal power consumed on the coil resistance of motor refers to the heat generated by the coil resistance in unit time
2. The total power consumed by the motor refers to the total electric energy consumed by the motor in unit time, the thermal power consumed by the motor coil resistance refers to the heat generated by the coil resistance in unit time, and the output power of the motor refers to the external mechanical power, that is, the external mechanical work in unit time
P heat = I ^ 2 * r * t
P electricity = UI = P heat + P Machinery
The rated current is the maximum power of the appliance when it is working normally for a long time. The actual power of electrical appliances is the electrical power consumed by electrical appliances in actual work. In order to ensure the normal operation of electrical appliances, the actual power should not be greater than its rated power. ... unfold
P heat = I ^ 2 * r * t
P electricity = UI = P heat + P Machinery
The rated power of electrical appliances is the maximum power of electrical appliances when they work normally for a long time, and it is also the electric power of electrical appliances when they work under rated voltage or rated current. The actual power of electrical appliances is the electrical power consumed by electrical appliances in actual work. In order to ensure the normal operation of electrical appliances, the actual power should not be greater than its rated power. Put it away
1) Given the perimeter 2p of a triangle, the area s of a right triangle is expressed as a function of a right side X by an analytic formula
Let the length of another right angle be y. then the hypotenuse is 2p-x-y
therefore
X^2+Y^2
=(2P-X-Y)^2
=4P^2-4P(X+Y)+(X+Y)^2
So y = 2p (P-X) / (2p-x)
So s = XY / 2 = PX (P-X) / (2p-x)
Let two right angle sides x y, then the hypotenuse is 2p-x-y
x^2 + y^2 = (2p-x-y)^2
The right side is equal to the solution
y= 2P(P-x)/(2P-x)
S=1/2 XY = Px(P-x)/(2P-x)
One side is x, the other side is 2S / X
Bevel = 2p-x-2s / X
(X+2S/X)^2=(2P-X-2S/X)^2
4P^2=4P(X+2S/X)
P=X+2S/X
2S=-X^2+XP
S=-1/2(X^2-2XP)
The tolerance of {an} is known to be d > 0, and a2a3 = 45, a1 + A4 = 14
(1) Finding the value of A1, D
(2) Find the first n times sum SN of sequence {an}
（1）∵a2a3=45,a1+a4==a2+a3=14
∴a2=5,a3=9 d=4
∴a1=1
∴an=1+(n-1)*4=4n-3
∴Sn=a1+a2+..+an
=4*1-3+4*2-3+...+4*n-3
=（4*1+4*2+...+4*n)-3n
=4*n*（n+1）/2-3n
=2n^2-n
The solution is an arithmetic sequence, so a1 + A4 = A2 + a3 = 14 and a2a3 = 45 d > o
So A2 = 5, A3 = 9
d=9-5=4 a1=a2-d=5-4=1
an=1+(n-1)*4
=4n-3
Sn=a1+a2+...+an=na1+n(n-1)d/2=n+n(n-1)*4/2=2n^2-n
a2a3=45，a1+a4=14
a1=1
an=4n-3
Sn=4*n*（n+1）/2-3n=2n^2-n
How to calculate the electric power consumed by the motor?
Is it possible to use formulas such as P = w / T and P = UI-
The circuit of the motor is a non pure resistance circuit, so the consumed electric energy, that is, the work done by the current (w = UIT), is mainly converted into mechanical energy, and only part of it is converted into heat energy (q = I & # 178; RT), so w > Q, that is, uit > I & # 178; RT. therefore, the electric power consumed by the motor can be calculated by P = w / T or P = UI, but not by P = I & # 178; R or P = u & # 178 / R
The functional relationship between the area s of a circle and its perimeter C is
The area of the circle s = π R ^ 2
The girth C = 2 π r r = C / 2 π is substituted into the above formula
S=π*(C/2π)^2=C^2/(4π)
: ∵ perimeter L = 2 π R,
∴r=l÷2π，
The area of the circle = π R 2 = C 24 π
So fill in the blanks: S = C24 π
S=πr²
C=2πr
S=C²/4π
S=1/2*Cr
C=2∏R
S = Πr * r = Πr squared.
Then s = Π (C / 2 Π) squared
=(square C) / 4 Π
If the tolerance of arithmetic sequence an is greater than 0, the first term and Sn satisfy a2a3 = 45, a1 + A4 = 14, the first n term and Sn of the formula can be obtained
(A2) (A3) = 45 (A1) + (A4) = (A2) + (A3) = 14, the solution is: A1 = 5, A3 = 9, then: D = 4, thus: an = 4N + 1sn = [n (a1 + an)] / 2 = 2n & # 178; + 3N, then: BN = Sn / (n + C) = (2n & # 178; + 3n) / (n + C) because BN is an arithmetic sequence, then BN should be a function of degree about n