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As shown in the figure, points e, F, G and H are the midpoint of edges AB, BC, CD and Da of parallelogram ABCD respectively Verification: △ bef ≌ △ DGH
It is proved that ∵ quadrilateral ABCD is a parallelogram,
∴∠B=∠D，AB=CD，BC=AD．
And ∵ e, F, G and H are the midpoint of the four sides of the parallelogram ABCD respectively,
∴BE=DG，BF=DH．
∴△BEF≌△DGH．
As shown in the figure, points e, F, G and H are the midpoint of edges AB, BC, CD and Da of parallelogram ABCD respectively Verification: △ bef ≌ △ DGH
It is proved that ∵ quadrilateral ABCD is a parallelogram,
∴∠B=∠D，AB=CD，BC=AD．
And ∵ e, F, G and H are the midpoint of the four sides of the parallelogram ABCD respectively,
∴BE=DG，BF=DH．
∴△BEF≌△DGH．
It is known that in Zai trapezoidal ABCD, CD ‖ AB, ∠ a = 40 °, ∠ B = 70 °, test description ad = ab-dc
Proof: make CE ‖ AD and hand over AB to point E
Then the quadrilateral adce is a parallelogram
∴AD=CE,∠BEC=∠A=40°,AE=CD
∵∠B=70°
∴∠BCE=70°
∴CE=BE
∵BE=AB-AE=AB-CD
∴AD=AB-CD
It is known, as shown in the figure, in the trapezoidal ABCD, AB / / CD, ∠ a = 60 °, ∠ B = 45 °, DC = 2, ad = 4, calculate the area of the trapezoidal ABCD
As high De, CF in △ DAE, ∠ a = 60, ad = 4 ‡ AE = 2, de = 2, root number 3 = CF
In △ CFB, ∠ B = 45 ° BF = CF = 2 root numbers 3 ‡ AB = 4 + 2 root numbers 3
‡ s trapezoidal ABCD = 2 root numbers 3 * (2 + 4 + 2 root numbers 3) / 2 = 6 root numbers 3 + 6
Why is a matrix reversible, its row vector group is linearly independent, and its column vector group is also linearly independent?
Because if a is reversible, ax = 0 has a unique solution 0, and XA = 0 also has a unique solution 0, which is exactly the definition of linear independence between column vector group and row vector group
Let a and B be n * M-type and m * n-type matrices respectively, and C = AB be a reversible matrix. It is proved that the column vector group of B is linearly independent Specifically,
It is proved that R (c) = n is known reversibly by C
So n = R (c) = R (AB)
RELATED INFORMATIONS
- 1. 2. Let a be m × N matrix, B is n × M matrix, and m < n, ab = I is known, where I is an m-order identity matrix. It is proved that the column vector group of B is linear
- 2. Given that a = √ 2, B = 3, the included angle between a and B is 45 °, find the vector a+ λ B and λ When the included angle of a + B is an acute angle, λ Value range of
- 3. If the center angle of an arc is 135 °, and the arc length is equal to 3 times the circumference of a circle with a radius of 5cm, the radius of this arc is______ cm．
- 4. In ⊙ 0, if the length of string AB is equal to the radius, find the degree of the circumferential angle of the arc opposite string ab
- 5. In a circle with radius 1, the length is equal to What is the central angle of the string of 2______ Degrees
- 6. Given that the length of an arc on circle O is equal to the side length of the inscribed square of the circle, find the radians of the center angle of the circle to which this arc is opposite
- 7. In a circle, if the length of an arc is one fifth of the circle, the degree of the center angle of the arc
- 8. Radian formula A circle with a radius of 106820 is 12336 from any point to another point. Find its height, radian, and Xuan length. Write the formula,
- 9. The center angle of an arc is 250 °, and the arc length of the arc is equal to the circumference of a circle with a radius of 3cm. Calculate the radius of the arc
- 10. If the arc number of the center angle of the sector is 2 and the chord length of the sector arc is 2, the area of the sector is () A. 1 sin21 B. 2 sin22 C. 1 cos21 D. 2 cos22
- 11. Radian system formula about sector arc length and area formula? Derivation formula?
- 12. Given that the chord length of the center angle with radian number 2 is also 2, the arc length of the center angle is () A. 2 B. 2sin1 C. 2sin-11 D. sin2
- 13. A construction company wants to build an arc-shaped curve with a radius of 30m. The center angle of the arc-shaped curve is 120 °, then the length of the curve is? (π takes 3)
- 14. The radius of the circle is 240mm. How many degrees is the center angle of the circle opposite to the arc with a length of 500mm on the circle? Why is the answer only positive
- 15. It is known that the edge length of regular tetrahedron a-bcd is a (four faces are congruent regular triangles), e and F are the midpoint of edges BC and ad respectively. Find the angle formed by EF and ab
- 16. An ant starts from a, crawls along the polygon for a week and returns to point a, then vector AB + vector BC + vector CD + vector de + vector EF + vector FG + vector GA = ()
- 17. Arc length equals________ The central angle of the circle opposite the arc of is called the angle of 1 radian
- 18. There is a curve in the shape of an arc, as shown in the figure. The length of the curve is 12M, and the center angle of the arc is 81 °. Find the radius r of this arc as __ (accurate to 0.1M)
- 19. Using the arc length formulas under angle system and radian system respectively, the length of the arc corresponding to the 60 ° center angle in a circle with a radius of 1m is calculated
- 20. It is known that the arc length of an arc is equal to the side length of the inscribed regular triangle of its circle, then the radian number of the center angle of the arc is __