If f (x) = Sina cosx, then f '(a) is equal to If we use the formula of composite function: YX '= Yu' * UX ', that is, the derivative of y to X is equal to the product of the derivative of y to u and the derivative of u to x, how to calculate it?

If f (x) = Sina cosx, then f '(a) is equal to If we use the formula of composite function: YX '= Yu' * UX ', that is, the derivative of y to X is equal to the product of the derivative of y to u and the derivative of u to x, how to calculate it?

This is not a product relation. F '(x) = SiNx
f"(a)=sina

Let f (x) be an even function on R and a decreasing function on (- infinity, 0). If f (a) is greater than f (1), then the value range of real number a is——

Because f (x) is an even function, there is a
f(-x)=f(x),
Because the function is a decreasing function on (- infinity, 0), if X1 < x2 < 0, then - X1 > - x2 > 0, so
F (x1) > F (x2), so f (- x1) = f (x1) > F (x2) = f (- x2), so
If f (a) > F (1) = f (- 1), then a > 1 or a < - 1 is obtained

The function y = f (x) is an even function on R and an increasing function on (- ∞, 0]. If f (a) ≤ f (2), then the value range of real number a is ()
A. （-∞，2]B. [-2，+∞）C. [-2，2]D. （-∞，-2]∪[2，+∞）

∵ function y = f (x) is an even function on R, and it is an increasing function on (- ∞, 0], and it is a decreasing function on [0, + ∞). Then the inequality f (a) ≤ f (2) is equivalent to f (| a |) ≤ f (2), that is, | a | ≥ 2, and the solution is a ≥ 2 or a ≤ - 2

In integers 1-9, what numbers do a, B, C represent to make the following equation true?
c÷b=b÷a=a÷1
a=( ) b=( ) c=( )

c÷b=b÷a=a÷1=a
b=a²
c=ab=a³
So only a = 2
So a = 2, B = 4, C = 8

Equation: 10 (x + 2) + x-18 = 10x + X + 2, X is unknown

10（x+2)+x-18=10x+x+2 x
11x+2=13x
2x=2
x=1

The sum of two plus two plus two plus two plus three plus one-third plus three

How much is half root 2 plus half root 2 + root 3
=√2+√3；
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List the equation and find the solution of the equation. The sum of 5 times of a number and 2.5 is 25

Let this number be X
5x+2.5=25
5x=22.5
x=4.5
The answer is 4.5

Given Tan α = 3, Tan β = - 1 / 3, α ∈ (0, π / 2). β ∈ (π / 2, π), find α - β

tan(α-β )=(tanα-tanβ)/(1+tanα*tanβ)
cot(α-β )=1/tan(α-β )=0
And because
α∈(0,π/2).β∈(π/2,π),
So α - β = - π / 2

In the plane rectangular coordinate system, the coordinates of point P and Q are (5,0) and (0,3), respectively
In the plane rectangular coordinate system, if the coordinates of point P are (5,0) and point q are (0,3), the line segment PQ is translated 4 units to the right and 2 units to the up, and the line segment p1q1 is obtained, then the coordinates of points P1 and Q1 are?

P1 coordinate is: x = 5 + 4 = 9, y = 0 + 2 = 2, that is (9,2)
Q1 coordinates: x = 0 + 4 = 4, y = 3 + 2 = 5, that is (4,5)

How many hours is 40 minutes
emergency

2/3