What's 2.2 times 12 out of 11?

What's 2.2 times 12 out of 11?

2.2*12/11
=（2.2/11）*12
=0.2*12
=2.4

Given vector a = (3 / 2, SiNx) vector b = (cosx, 1 / 3), and vector a is parallel to vector B, what is the acute angle X
1. Vector a = (3 / 2, SiNx) vector b = (cosx, 1 / 3), and vector a is parallel to vector B
2. So (3 / 2) * (1 / 3) - cosx * SiNx = 0
3. So 1 / 2 = sinxcosx
4. So 1 = sin2x
5. So 2x = 2K π + π / 2
So x = k π + π / 4
7 and X is an acute angle
8, so x = π / 4. This is what I see from other places. I don't know how to get it from 3 to 4.5 steps, especially from 3 to 4. I really want to forget some knowledge points. Can you explain it to me in detail

If 2 is multiplied by both sides of 3, i.e. 1 = 2sinxcosx, we also know that 2sinxcosx = sin2x
Suppose t = 2x, then Sint = 1. From its image, when t = π / 2, Sint = 1
It is also known that one period is 2 π, so t = 2x = 2K π + π / 2

74 times 0.68 divided by 2.68

=11×1.34×0.68÷(2×1.34)
=11×0.68÷2
=11×0.34
=3.74

It is known that the parabola C1: y ^ 2 = 4PX (P > 0), the focus is F2, its quasilinear and X axis intersect at the point F1, the ellipse C2 takes F1 and F2 as the left and right focus respectively, and its eccentricity e = 1 / 2, and one intersection point of parabola C1 and ellipse C2 is denoted as M. when p = 1, the standard equation of ellipse C2 is solved

p=1
y²=4x
So the focus is (4 / 4,0), that is (1,0)
Guide line x = - 1
So the ellipse has C = 1
e=c/a=1/2
So a = 2
So B & sup2; = A & sup2; - C & sup2; = 3
a²=4
The focus is on the x-axis
So x & sup2 / 4 + Y & sup2 / 3 = 1

Seven times nine plus twelve divided by three equals 91

7*（9+12/3）
=7*13
=91

As shown in the figure, the parabola y = - x2 + 2x + m (m < 0) intersects the X axis at points a (x1, 0) and B (X2, 0), and point a is on the left side of point B. when x = x2-2, y______ 0 (fill in ">" = "or" < "

∵ the parabola y = - x2 + 2x + m (m < 0) intersects the x-axis at points a (x1, 0), B (X2, 0), ∵ X1 + x2 = 2, x1x2 = - M > 0, ∵ X1 > 0, X2 > 0, ∵ X1 + x2 = 2 ∵ X1 = 2-x2 ∵ x = - X1 < 0 ∵ y < 0, so the answer is ∵

A number divided by 4 plus 3 is equal to the number divided by 5 plus 4?

x÷4+3=x÷5+4
The solution is x = 20

Given that circle O1 is tangent to circle O2, O1O2 = 5, then the radius of circle O2 is?

Is there no other known condition? If there is no other condition, the radius of O2 is (5 minus the radius of O1) or (the radius of O1 minus 5) or (the radius of O1 plus 5)

30 page answers to supplementary exercises of mathematics in Grade 6

1) 3.6:3 6:6
2）6:6
3) No
Second, can we
Three 2:5 20:50
5. The second one is OK and the first one is not

-The third power of a times (- AB)

=a^4 b^3