C expression types (assignment expression, arithmetic expression, relational expression, logical expression, conditional expression, comma expression) and evaluation rules

C expression types (assignment expression, arithmetic expression, relational expression, logical expression, conditional expression, comma expression) and evaluation rules

C language operators and their priority table pithy formula round down arrow a dunhao special increase and decrease, rich and strong needle long three times division, four addition and subtraction, five shift, do not forget the fish, it is in the kitchen, the small lamp headlight does not wait for father to feed the fish, uncle doubt, naked chicken also doubt thirteen aunt, fourteen father, fifteen tease, pocket to low "round down arrow a dunhao"

In C + +, the value of () is not a logical value in the following expressions: a arithmetic expression; B relational expression; c logical expression; D comma expression
Why do I think a and D can be chosen

A comma expression has a value, which cannot be replaced by a statement. The value of a comma expression is the value of the nth subexpression, that is, the value of the expression n
int a,b,c,d；
d=(a=1,b=a+2,c=b+3)；
cout

The base of a triangle is twelve centimeters long. If the height remains the same, the area will be increased by sixteen square centimeters after the base is extended by four centimeters

Solution: the area ratio of triangles with the same height is equal to the ratio of the bottom
That is, the ratio of the original triangle area to the newly added triangle area is 12:4 = 3:1
Therefore, the original triangle area is: 16 * 3 = 48 (square centimeter)
(Note: you can also use the area of the new triangle to calculate the height of 8, and then calculate the area of the original triangle to be 48 square centimeters.)

Solve equation 4.2-0.2x = 0.5 (24-x)

4.2-0.2x=0.5(24-x)
4.2-0.2x=12-0.5x
0.5x-0.2x=12-4.2
0.3x=7.8
x=26

The circumference of a semicircle is 20.56 cm. What is the area of the semicircle

20.56÷（3.14÷2+1）
=20.56÷（1.57+1）
=20.56÷2.57
=8（cm）
8÷2=4（cm）
3.14×4²÷2
=3.14×16÷2
=50.24÷2
=25.12（cm²）
A: the area of this semicircle is 25.12 square centimeters
I'm glad to answer for you

25×3.2×1.25．

25×3.2×1.25，=25×4×（0.8×1.25），=100×1，=100．

As shown in the figure, △ ABC, the angular bisectors ad, be and CF intersect at point h, Hg ⊥ AC is made through point h, and the perpendicular foot is g, then ∠ ahe = ∠ CHG? Why?

Reasons: ∵ ad, be and CF are bisectors of △ ABC. Suppose ∵ bad = ∵ CAD = x, ∵ Abe = ∵ CBE = y, ∵ BCF = ∵ ACF = Z, then 2x + 2Y + 2Z = 180 ° i.e. x + y + Z = 90 ° in △ AHB, ∵ ∵ ahe is the outer angle of △ AHB, ∵ ahe = ∵ bad + ∵ Abe = x + y = 90 ° - Z in △ AHB

Let A1, A2 ,an,b1,b2,… , BN are real numbers and B1 ^ 2-b2 ^ 2 - -bn^2>0
Verification (A1 ^ 2-A2 ^ 2 -...) -an^2)(b1^2-b2^2-… -bn^2)
I know I can't - that's why I asked. I can't prove this.

A1 ^ 2-A2 ^ 2... - an ^ 20 let y = (a1x + B1) ^ 2 - (a2x + B2) ^ 2... - (anx + BN) ^ 2 = (A1 ^ 2-A2 ^ 2... - an ^ 2) x ^ 2 + 2 (a1b1-a2b2... - anbn) x + (B1 ^ 2-b2 ^ 2... - BN ^ 2) Cauchy inequality is proved by the discriminant less than or equal to zero because it is always greater than or equal to zero

If the similar area ratio of the two triangles is 1:4, then the ratio of the corresponding median line is

1：2

It is proved that the function f (x) = x + lgx has zeros on (0,1)
To complete the process

Certification:
Firstly, a derivation formula is proved
y = lgx = [lnx]/ln10
∴ dy/dx = 1/xln10
Back to the theme:
f(x) = x + lgx
df/dx = 1 + 1/xln10
When x ∈ (0,1), DF / DX > 0
F (x) is an increasing function
∵ when X -- > 0, lgx -- > - ∞
When X -- > 0, f (x) -- ∞
∵ when X -- > 1, f (x) -- > 1 + 0 = 1 > 0
On (0,1), the continuous smooth differentiable function f (x) has one end below the x-axis and one end above the x-axis
F (x) has zero on (0,1)