1. In the cube abcd-a1b1c1d1, find the tangent of the angle between BB1 and bc1d1 Don't worry about children who don't know= If it's 1, I won't ask

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• 1. If AB = 2, CD = 4, EF ⊥ AB, then the degree of the angle between EF and CD is () A. 90°B. 45°C. 60°D. 30°
• 2. First: the side length of square ABCD is 1, e and F are the midpoint of BC and CD respectively, and they are folded into a triangular pyramid along AE, EF and AF, so that the three points B, C and D coincide. Then the volume of this triangular pyramid is? Second: in the cube abcd-a1b1c1d1, e, F, G and H are the midpoint of BC, CD, CC1 and c1d1 1. Verification of a1g vertical plane efc1 2. Verification of BH parallel plane efc1 The picture should be drawn by oneself, ha ha
• 3. In p-abcd, PA = AC = 2, Pb = PD = geng6, (2) Given that point E is on PD, PE: ed = 2:1, and point F is the midpoint of edge PC, it is proved that BF is parallel to plane AEC
• 4. 1.S=a^n+a^(n-1)b+a^(n-2)b^2+…… +ab^(n-1)+b^n（n∈N*,ab≠0） 2. Given that the general term formula of the sequence {an} is an = {- 6N + 5 (n is odd), find the first n terms and Sn of the sequence {2 ^ n (n is even)
• 5. (1) Find arithmetic sequence 8, 5, 2 (2) judge whether - 401 is an arithmetic sequence - 5, - 9, - 13 What's your item? If yes, which item is it? If not, explain the reason
• 6. Given the function f (x) = 2Sin (Wx + π / 6), w ∈ R, and w ≠ 0.1, if the image of F (x) passes through the point (π / 6,2) and 0 ＜ w ＜ 3, find the value of W. 2. Under the condition of the first question, sun function g (x) = MF (x) + n (m ＞ 0), when x ∈ [0, π / 2], what is the range of G (x)
• 7. In the plane rectangular coordinate system, points a (1,1), B (4,2), C (2,3). 1 seek the coordinates of vector AB (with arrow) + AC (with arrow), 2 seek the angle α of vector AB (with arrow) and AC (with arrow)
• 8. The function f (x) = - x2 + 2aX + 1-A has the maximum value 2 in the interval [0,1]. Find the value of real number a
• 9. On the vector problem! D. E and F are the moving points of the edges AB, BC and Ca of △ ABC, respectively Starting from a, B and C, they move along each side to B, C and a at a certain speed, When t = 1, it reaches B, C and a respectively, Proof: at any time of 0 ≤ t ≤ 1, the center of gravity of △ def remains unchanged The center of gravity is the intersection point of the center, which is proved by vector
• 10. 1 1 Is the function y = x (-- + -) odd or even? X of 2 + 1 2
• 11. Let the side length of the upper and lower sides of a regular triangular platform be 2cm and 5cm respectively, and the side edge length be 5cm
• 12. The number of solutions of the equation SiNx = 10 / X is The main answer is to tell me the method
• 13. The number of solutions to the equation SiNx = x
• 14. Equation 3 / X-2 = 5 / X
• 15. The interval of solution of equation 2x + X-2 = 0 is () A. （-1，0）B. （0，1）C. （1，2）D. （2，3）
• 16. Solve the equation LG (x + 1) + LG (X-2) = LG4?
• 17. I hope the teacher can explain It is known that the function f (x) whose domain is [0,1] satisfies the following three conditions at the same time 1. For any x ∈ [0,1], there is always f (x) ≥ 0 2、f（1）=1 3. When x ≥ 0, y ≥ 0, and X + y ″ 1, f (x + y) ≥ f (x) + F (y) (1) Try to find the value of F (0) (2) . find the maximum of F (x) (3) It is proved that when x belongs to [1 / 4,1], there is always 2x ≥ f (x)
• 18. High school function problem, please specify the steps to solve the problem: If f (x) = (x ^ 2) + log (under x + root (1 + x ^ 2)), and f (2) = 3, then f (- 2) =?
• 19. What is the definition of high school function
• 20. Let a and B be a set of nonempty numbers, and F: X → y be a corresponding rule from a to B. then the mapping f: a → B from a to B is called a function, denoted as y = f (x), where x ∈ a, y ∈ B, the original image set a is called the definition field of function f (x), and the image set C is called the value field of function f (x). Obviously, there is C ∈ B Why is it that the elements in the image set C ∈ B, not to say that B is the range of the function f (x), can remain?