Simple calculation: (4 / 7 * 9 / 10 * 11 / 4) / (2 / 11 * 7 / 2 * 9 / 5)

Simple calculation: (4 / 7 * 9 / 10 * 11 / 4) / (2 / 11 * 7 / 2 * 9 / 5)

(8/9+10/7+6/11)/(3/11+5/7+4/9)=2
Numerator and denominator are all * 7 * 9 * 11
Typing is not easy,

sinπ/8×cosπ/8

sin(π/8)×cos(π/8)
＝(1/2)×sin(π/4)
＝(1/2)×(√2)/2
＝(√2)/4
(double angle formula)
sin2α＝2sinαcosα）

It is known that BD is a middle line of triangle ABC. If the circumference of abd and BCD are 21 and 12, then AB.BC Long?

AB+BD+AC/2=21
BC+BD+AC/2=12
AB-BC=21-12=9

In the triangle ABC, the opposite sides of angles a, B and C are a, B and C respectively. If a, B and C form an arithmetic sequence, B = 30 degree
If the area of triangle is 2 / 3, then B=
2 in the triangle ABC, a = 5, B = 4, cos (a-b) = 31 / 32, then COSC=
3. Quadratic equation AX ^ - (2) BX + C = 0, where a, B and C are the three sides of obtuse triangle, and B is the longest
a. It is proved that the equation has two real roots
b. Prove that two real roots are integers
c. If a = C, try to find the change range of the absolute value of the two differences
Note: (2) stands for root 2, hope to have specific steps

1. From the problem, we get 2B = a + C, ∠ B = 30 °, s = (1 / 2) ac * SINB = 1.5, ∵ AC = 6, ∵ CoSb = (a ^ 2 + C ^ 2-B ^ 2) / (2Ac) = [(a + C) ^ 2-B ^ 2-2ac] / (2Ac) = (3b ^ 2-12) / 12 = (b ^ 2-4) / 4 = √ 3 / 2 ∵ B ^ 2 = 4 + 2 √ 3 = (1 + √ 3.2, method 1 ∵ a ＞ B, ∵ a ＞ B

Finding the domain of definition and value of y = arcsin (x ^ 2-3x + 3)

X ^ 2-3x + 3 should be greater than negative one and less than positive one,
Because x ^ 2-3x + 3 itself is a function greater than 0.75, it is not equal to x ^ 2-3x + 3

The length and width of a rectangle are increased by 9 meters respectively, and the area is increased by 720 square meters. How many meters is the perimeter of the original rectangle?

Length x width y XY + 720 = (x + 9) (y + 9) 720 = 9x + 9y + 81 9 (x + y) = 720-81 x + y = 71 perimeter 142

Noh / A-1 / + (B + 2) square = 0, find the value of the square of ab-b (a-b) + (AB) cube?
Ask for a netizen. See answer

Because / A-1 / > = 0, (B + 2) ^ 2 > = 0
/A-1 / = 0, (B + 2) ^ 2 = 0
a=1,b=-2.
I'm not clear about the landlord's problem. Please explain

If B (B is not equal to 0) is a root of the equation about x square + ax-6b = 0 of X, then the value of a + B is

Substituting x = B into the equation of x square + ax-6b = 0, we get
b²+ab-6b=0
∵b≠0
Divide both sides by B
b+a-6=0
That is, a + B = 6

It's a two word word that describes hard work

Racking one's brains, doing one's best, wasting one's efforts

The volume of a cone is 12 cubic decimeters, the height is 3 decimeters, and the bottom area is () square decimeters

v=1/3sh
S = V / 1 / 3 / h = 12 / 1 / 3 / 3 = 12 square decimeters