In the tetrahedral o-abc of high school mathematics, OA = vector a, OB = vector B, OC = vector C, e is the midpoint of AD, D is the midpoint of BC, and the vector a, B, C is used to represent the vector OE

Vector od = 1 / 2 vector B + 1 / 2 vector C, vector OE = 1 / 2 vector a + 1 / 2 vector OD, so vector OE = 1 / 2 vector a + 1 / 2 vector B + 1 / 2 vector C

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1. The known vector a + B = 2i-8j Given the vector a + B = 2i-8j, A-B = - 8i + 16J, the problem of finding a * B does not tell that I and j are unit vectors
2. Under the combined action of forces F1, F2, F3 and F3, the object moves in a straight line at a constant speed. If the external force F1 is suddenly removed, the motion of the object is () A. It is necessary to make a uniform acceleration linear motion along the direction of F1. B. It is necessary to make a uniform deceleration linear motion along the direction of F1. C. It is still a uniform linear motion. D. it may be a linear motion or a curve motion
3. The object moves in a straight line at a constant speed under the action of common point forces F1, F2 and F3. The correct value of these three forces is () A. 15N、5N、6NB. 1N、2N、10NC. 3N、4N、5ND. 1N、6N、3N
4. The object with mass m moves in a uniform straight line under the action of three common forces F1, F2 and F3 Keeping F1 and F2 unchanged, it's impossible to change the F3 direction by 90 degrees A uniform linear motion B-uniform acceleration linear motion C uniform deceleration linear motion D-uniform variable speed curvilinear motion
5. When an object moves in a straight line at a constant speed under the action of F1, F2, F3 and FN, if the force F2 is suddenly removed, how will the object move?
6. Given that the absolute values of the three forces F1, F2 and F3 are equal, all = 1, and the sum of the three forces is 0, what is the absolute value of F1-F2?
7. Given that the forces F1, F2 and F3 satisfy | F1 | = | F2 | = | F3 | = 1, and F1 + F2 + F3 = 0, then | F1-F2 | = 1 Plane vector problem >
8. A particle is in equilibrium under the action of three forces F1, F2 and F3 (unit: Newton) on the plane. Given that F1 and F2 form an angle of 60 ° and the sizes of F1 and F2 are 2 and 4 respectively, the size of F3 is 0______ ．
9. A body is in a state of uniform linear motion under the combined action of several constant forces. If one F1 suddenly stops acting and the other forces remain unchanged, then () A. The object continues to move in a straight line at a constant speed. B. the object will be stationary. C. the speed of the object's motion must remain unchanged. D. the direction of the object's motion may remain unchanged
10. The object is in equilibrium under the action of several constant forces. If another constant force is applied to the object, the object may do () A. Stationary or uniform linear motion B. uniform linear motion C. curvilinear motion D. uniform curvilinear motion
11. Vector a is equal to (2k, 1), vector B is equal to (3, - 2), and vector A / / vector B, find the value of real number K
12. Given the vector a = (1, K), B = (2k, m) and a ⊥ B, / A / = / B /, find the value of real number k, M 2. Vector a + vector b 3. / vector a + vector b/
13. Given (a ^ 2-3a-1) + (a ^ 2-5a-6) * I = 3, find the value of real number a
14. As shown in the figure, point I is the inner part of triangle ABC, the extension line of line AI intersects the circumcircle of triangle ABC at point D, and intersects the edge of BC at point E. prove that id = BD, BD square equals Da times EA The second question is more important!
15. As shown in the figure, the triangle ABC is the inscribed triangle of circle O, I is the inner part of triangle ABC, the extension line of AI intersects BC at point E, and intersects circle O at point D Come on, now, now!
16. Given that | BC | = 2 in triangle ABC and point P satisfies AP vector = XAB vector + YAC vector, if x, Y > = 0, x + y = 1 / 2, then the length of the graph formed by P is? Don't understand what the last question is?
17. I is the heart of △ ABC, AC = 2, CB = 3, Ba = 4, AI vector = XAB vector + YAC vector, then x + y =?
18. In the triangle ABC, AC is 2, AB is 4, CB is 3, I is the heart, AI is XAB plus YAC, x plus y is what
19. In the triangle ABO, vector OA = vector a, vector ob = vector B, M is the midpoint of ob, n is the midpoint of AB, P is on, the intersection of am, then what is AP equal to? Options: A 2 / 3 vector A-1 / 3 vector b B - 2 / 3 vector a + 1 / 3 vector b C 1 / 3 vector A-2 / 3 vector b D - 1 / 3 vector a + 2 / 3 vector b
20. It is known that the equation of parabola is y ^ 2 = 4x, the line L passes through the fixed point P (- 2,1), and the slope is K. when the value of K is, there is a common point between the line L and the parabola It is known that the equation of parabola is y ^ 2 = 4x, the straight line L passes through the fixed point P (- 2,1), and the slope is K. when the value of K is, the straight line L and parabola have one common point; there are two common points, but there is no common point