There are 13 Science and technology books in our bookcase, half of them are story books, and the rest are comic books. How many are comic books?

There are 13 Science and technology books in our bookcase, half of them are story books, and the rest are comic books. How many are comic books?

1-13-12, = 23-12, = 16

Find the total differential Du of the function u = f (2x ^ 2-y ^ 2, XY)

Let u = 2x ^ 2-y ^ 2, v = XY
Then chain guide rule!

How to calculate 34.7 * 69 + 65.3 * 31 + 30.6 * 19 with a simple method

34.7*69+65.3*31+30.6*19
=34.7*69+34.7*31+30.6*31+30.6*19
=100*34.7+50*30.6
=3470+1530
=5000

How to calculate the general term formula, 1,1,3,3,5,5,7,7

This sequence is obtained by subtracting two sequences
1,2,3,4,5,6,7,8,9,10.
0,1,0,1,0,1,0,1,0,1.
Obviously, the general formula of the first sequence is a (n) = n
The general formula of the second sequence is a (n) = (- 1) ^ n + 1) / 2
So the general term formula of the original sequence is a (n) = n - (- 1) ^ n + 1) / 2

The partial derivative of Z = x / (x2 + Y2) (where 2 is the square)

The partial derivative of Z to X: treat y as a constant
Partial Z / partial x
=[（x2+y2）-x(2x)]/[（x2+y2）2]
=[y2-x2]/[(x2+y2)2]
The partial derivative of Z to Y: take x as a constant
Partial Z / partial y
=-2xy/[（x2+y2）2]

If the concentration and temperature of acetic acid are changed, the dissociation degree and dissociation constant are changed
I hope you can help me find out the exact change trend and reasons,

The higher the concentration of acetic acid, the lower the ionization degree and the same ionization constant
When the concentration of acetic acid is constant, the higher the temperature is, the greater the ionization degree and ionization constant are

Physical mechanical efficiency involves all the formulas, as well as the relationship between pulley and mechanical efficiency

1. Speed: v = s / T2, lever balance condition: F1 L1 = F2 L2 3, ideal slope: F / g = H / L 4, ideal pulley: F = g / N 5, actual pulley: F = (G + G dynamic) / N (vertical direction) 6, work: w = FS = GH (lifting objects high) 7, power: P = w / T = FV 8, principle of work: W hand = w machine 9

What is the θ of function f (x) = e ^ X in the finite increment formula of interval [0,1]? How to find it? The answer is ln (E-1)

Since e ^ 1-e ^ 0 = f '(θ) (1-0), and f' (x) = e ^ x, E-1 = e * θ, θ = ln (E-1)

The strongest solar radiation at the following latitudes are: A, 5 degrees north latitude B, 25 degrees south latitude C, 60 degrees north latitude D and 9 degrees south latitude
The strongest solar radiation is at the following latitudes:
A. 5 degrees north latitude
B. 25 degrees south latitude
C. 60 degrees north latitude
D. 90 degrees south latitude
Please

The answer is a. because the lower the latitude, the closer to the equator, the stronger the radiation

A and B are two adjacent natural numbers. What is the greatest common factor of a and B______ ．

A and B are two adjacent natural numbers. The greatest common factor of a and B is 1