As shown in the figure, given that the sphere o is the inscribed sphere of cube abcd-a1b1c1d1 with edge length of 1, the cross-sectional area of plane acd1 truncated sphere o is () A. π6B. π3C. 66πD. 33π

As shown in the figure, given that the sphere o is the inscribed sphere of cube abcd-a1b1c1d1 with edge length of 1, the cross-sectional area of plane acd1 truncated sphere o is () A. π6B. π3C. 66πD. 33π

According to the meaning of the title, plane acd1 is an equilateral triangle with side length of 2, so the area of the cross-section obtained is the area of the inscribed circle of the equilateral triangle. From the figure, if the radius of the inscribed circle of △ acd1 is 22 × Tan 30 ° = 66, then the area of the cross-section obtained is π × 66 × 66 = π 6

Arrange natural numbers from small to large, try to find: (1) the sum of the first 10 items; (2) the sum of the first 100 items; (3) the sum of the first n items
Natural numbers seem to include 0

45,4950
The formula is sum = (0 + n-1) * n / 2
It's the same thing

If set a = {x | - 2 ≤ x ≤ a}, B = {y | - y = 2x + 3, X ∈ a}, C = {y | - y = X2, X ∈ a}, and C is contained in B, then the value range of real number a is

B={x| |-1≤x≤2a+3}
(1) When - 2 ≤ a ≤ 0,
C={z| a²≤ z ≤4}
So 4 ≤ 2A + 3,
A ≥ 1 / 2 is contradictory to - 2 ≤ a ≤ 0
(house)
(2) At 02:00,
C={z| 0≤ z ≤a²}
So a & # 178; ≤ 2A + 3,
-1 ≤a≤3
SO 2

1.84 / (18.4 / 0.5)

1.84/(18.4/0.5)
=1.84*0.5/18.4
=0.5/10
=0.05

4. If the length of two right sides of a right triangle is 6 and 8 respectively, the length of the third side is
4. If the length of two right sides of a right triangle is 6 and 8 respectively, the length of the third side is
5. In a right triangle, the degree to which the bisectors of two acute angles intersect to form an obtuse angle is____ .
6. It is known that the waist length of an isosceles triangle is 6cm and the base length is 8cm, then the perimeter of a triangle with the midpoint of each side as the vertex is 6cm____ 48_____ cm.
7. The result of factoring a ^ 3 + AB ^ 2-2a ^ B is____ .

The square of the hypotenuse = the sum of the squares of two right angle sides, so hypotenuse = 10
In RT triangle, two acute angles complement each other, so the degree of the bisector of two acute angles intersecting into an obtuse angle is_ 180-45 = 135 degrees
The fundamental median theorem of question 6 shows that the circumference of a triangle = half of 6 + 6 + 8 is the circumference = 10
You may have made a mistake in question 7, but the answer should be a (a-b) ^ 2

12-3 (x + 1) = 6-2 (x + 2), how to solve the equation

12-3（X+1)=6-2(X+2）
12-3x-3=6-2x-4
9-3x=2-2x
x=7

Tangent equation and normal equation of curve X = t + 1 y = T ^ 3 at t = 2

When t = 2
x=3,y=8
dy/dx=(3t^2dt)/dt=3t^2=12
So the tangent equation is:
12(x-3)-(y-8)=0
That is 12x-y-28-0
The normal equation is x + 12y-99 = 0
Hope to help you!

Are positive fractions, negative fractions and negative integers rational numbers

No! Finite is rational number

Finding the extremum of function f (x) = e ^ x + X & # - x

f'(x)=e^x+2x-1
∵ f '(x) monotonically increasing
The f '(x) has only one zero point
F '(x) = 0, the solution is x = 0
In (- ∞, 0): F '(x)

Because five out of nine times nine out of five equals one, five out of nine is reciprocal and nine out of five is reciprocal
It took Xiaoming 10 minutes and dad 8 minutes to walk the same way. The speed ratio between Xiaoming and dad is 4:5
A circle with a radius of 2cm has the same perimeter and area
Judge right and wrong, correct the wrong, and hit the right

1. Wrong, the concept of reciprocal is relative, and it should appear in pairs. Five out of nine is the reciprocal of nine out of five, or five out of nine and nine out of five are reciprocal
2. Wrong, we can only say that the average speed ratio of Xiaoming and dad is 4:5
3. Yes