Then the total differential of DZ, Z | x = 1, y = 1 is

Then the total differential of DZ, Z | x = 1, y = 1 is

dz=[sin(xy)+xycosxy]dx+(x^2cosxy)dy
dz | (1,1)=(sin1+cos1)dx+cos1dy

Solve the equations ay + BX = C, CX + AZ = B, BZ + CY = a

A: from 1, we get: y = (c-bx) / A, from 2, we get: z = (b-cx) / A, we get: B (b-cx) / A + C (c-bx) / a = a, we get B & # 178; - BCX + C & # 178; - BCX = A & # 178; so x = (B & # 178; + C & # 178; - A & # 178;) / (2BC) so y = (C & # 178; + A & # 178; - B & # 178;) / (2Ac) z = (a)

It is known that SN is the sum of the first n terms of the arithmetic sequence {an}. If S1 = 1, s4s2 = 4, then the value of s6s4 is ()
A. 94B. 32C. 54D. 4

From S1 = A1 = 1, s4s2 = 4, we get 4 + 6D2 + D = 4, the solution is d = 2, then s6s4 = 6A1 + 15d4a1 + 6D = 3616 = 94

It is known that: (ay BX) &# 178; + (BZ CY) &# 178; + (Cx AZ) &# 178; = 0. To prove: X / A + Y / B + Z / C

Because (ay BX) & 178; + (BZ CY) & 178; + (Cx AZ) & 178; = 0
So ax by = 0, BZ CY = 0, CX AZ = 0
So AX = by BZ = CY CX = AZ
So x / a = Y / b = Z / C

How to simplify the operation of 13 out of 19 and 14 times negative 11?

13 of 19 and 14 × 11
=19×（-11）+13/14×（-11）
=-201+（-143/14）
=-211 and 3 / 14

The volume of a cone is equal to () of the volume of its cylinder () and the formula is ()

It's not fun,
The volume of a cone is equal to (1 / 3) of the volume of a cylinder with equal base and height. The formula is (v = 1 / 3 SH)

Why can Taylor formula express some functions?

Because some functions can be expressed by expressions or infinite series

Physical meaning of specific heat capacity of water

When the temperature of 1kg water increases (or decreases) 1 ℃, 4200j heat is absorbed (or released)

Newton's second law says causality, that is, force is the factor that produces acceleration. So the expression should be a = f / m, why it is now expressed as F = ma. How to explain this expression in the physical sense

On the left side of the equation is the external force applied to the object, which belongs to the external attribute. On the right side of the equation are the mass and acceleration of the object, which belong to the attribute of the object itself. The equal sign separates the inside from the outside. I guess so. Newton's second law does not apply to the case of M = 0, and there is no concept of force on photons or extreme relativistic particles

On the inequality of logarithmic function
ln(x)-1

lnx