Line segment proof: known: point C is a point on line segment AB, and 3aC = 2Ab, D is the midpoint of AB, e is the midpoint of CB, de = 6, find the length of ab Why is be = 1 / 3bC = 1 / 6ab in this question?

It has been concluded that BC = 1 / 3AB
∵ e is the midpoint of BC
∴BE＝1/2BC＝1/2×（1/3AB）＝（1/2×1/3）AB＝1/6AB

Prove that the following matrix / model is an orthogonal matrix (model)
cos a - sin a 0
sina a cos a 0
0 0 1
--------------------------
Original title:
Show that the matrix
--------------------------
cos a -sin a 0
sin a cos a 0
0 0 1
------------------------
is an orthogonal matrix.
----->- > Cramer's rule, Gaussian eliminaton with row pivoting or matrix method may be used

Let the original matrix be a
A*A'=[cos a - sin a 0] [cosa sina 0]
[sina a cos a 0] * [-sina cosa 0]
[0 0 1] [0 0 1]
=[1 0 0]
[0 1 0]
[0 0 1]
=E
So according to the definition of orthogonal matrix, a is orthogonal matrix

What are divisors? (mathematical) what are all divisors of 10（

Definition
The quotient obtained by dividing an integer a by an integer B (B ≠ 0) is exactly an integer and has no remainder. We say that a can be divided by B, or B can divide A. A is called a multiple of B, and B is called a divisor (or factor) of A
The divisor of ten is 1,2,5,10

Let f (x) = SiNx cosx + X + a if 0

f'(x)=cosx+sinx+1=√2sin(x+π/4)+1
π / 4 ≤ x ≤ π / 2 √ 2 / 2 ≤ sin (x + π / 4) ≤ 1, so f '(x) is greater than 0 in this interval and is a monotone increasing function
F (0) = - 1 + A0, so there is only one point 0 in this interval

What is the plural of roof?

1.The plural of roof is roofs or rooves."Rooves" is an older form of the word and rarely used these days.Australian children right up to the 1980s,for example,were brought up with the word "rooves" ra...

There are 22 students participating in mathematics extracurricular activity group, 18 students participating in physics extracurricular activity group, 16 students participating in chemistry extracurricular activity group, and 36 students participating in at least one subject extracurricular activity group?

36 = 36 = 22 + 18 + 16-card (a ∩ b) - Card (a ∩ C) - Card (B ∩ C) + card (a ∩ B ∩ C) so card (a ∩ B ∩ B ∩ C) 36 = 36 = 22 + 18 + 16-card (a

Line segment proof: known: point C is a point on line segment AB, and 3aC = 2Ab, D is the midpoint of AB, e is the midpoint of CB, de = 6, find the length of ab Why is be = 1 / 3bC = 1 / 6ab in this question?