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slavikrds [6]
2 years ago
15

Ms. berkin is dividing her 4 1/2-foot by 6-foot bulletin board into 4 sections with ribbon stretched from each corner to the opp

site corner. How much ribbon does she need?

Mathematics
1 answer:
Mnenie [13.5K]2 years ago
3 0

Answer:

15 feet.

Step-by-step explanation:

A bulletin board has been shown in the figure below.

Where the width of the board AB = DC = 4\frac{1}{2} = 4.5 feet

and the length of the board AD = BC = 6 feet

As Ms. Berkin is dividing the board by stretching the ribbons to the opposite corners so the length of ribbons will be AC and BD.

In right angle triangle <em>ADC</em>, using Pythagorean Theorem,

AC^2=AD^2+DC^2  = 6^2+4.5^2=36+20.25=56.25

AC= \sqrt{56.25} = 7.5 feet

Similarly in triangle <em>BDC</em>,

BD^2=BC^2+DC^2 = 6^2+4.5^2=36+20.25 =56.25

BD=\sqrt{56.25} = 7.5 feet

Thus, total length of the ribbon used = AC + BD = 7.5 + 7.5 = 15 feet

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lord [1]

I suppose

H=\mathrm{span}\{10x^2+4x-1,3x-4x^2+3,5x^2+x-1\}

The vectors that span H form a basis for P_2 if they are (1) linearly independent and (2) any vector in P_2 can be expressed as a linear combination of those vectors (i.e. they span P_2).

  • Independence:

Compute the Wronskian determinant:

\begin{vmatrix}10x^2+4x-1&3x-4x^2+3&5x^2+x-1\\20x+4&3-8x&10x+1\\20&-8&10\end{vmatrix}=-6\neq0

The determinant is non-zero, so the vectors are linearly independent. For this reason, we also know the dimension of H is 3.

  • Span:

Write an arbitrary vector in P_2 as ax^2+bx+c. Then the given vectors span P_2 if there is always a choice of scalars k_1,k_2,k_3 such that

k_1(10x^2+4x-1)+k_2(3x-4x^2+3)+k_3(5x^2+x-1)=ax^2+bx+c

which is equivalent to the system

\begin{bmatrix}10&-4&5\\4&3&1\\-1&3&-1\end{bmatrix}\begin{bmatrix}k_1\\k_2\\k_3\end{bmatrix}=\begin{bmatrix}a\\b\\c\end{bmatrix}

The coefficient matrix is non-singular, so it has an inverse. Multiplying both sides by that inverse gives

\begin{bmatrix}k_1\\k_2\\k_3\end{bmatrix}=\begin{bmatrix}-\dfrac{6a-11b+19c}3\\\dfrac{3a-5b+2c}3\\\dfrac{15a-26b+46c}3\end{bmatrix}

so the vectors do span P_2.

The vectors comprising H form a basis for it because they are linearly independent.

4 0
2 years ago
In triangle XYZ, XY = 13, YZ=20, and XZ=25. What is the measure of angle Z to the nearest degree?
anastassius [24]
We can use Law of Cosines to solve for the angle of Z. The solution is shown below:
cos C=(a²+b²-c²)/2ab
cos Z = (yz² + xz² - xy² )/2*yz*xz
cos Z = (20² + 25  - 13²)/2*20*25
cos Z = 856 / 1000
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The answer is angle 31.13°. 
4 0
2 years ago
If 49x2 + 28x - 10 is rewritten as p2 + 4p -10, what is p in terms of<br> p=
madam [21]

Answer:

p=7x

Step-by-step explanation:

49x^[2] + 28x - 10 = p^[2] + 4p -10

This equation is in the form a^[2]x + bx + c.

<u><em>The 'c' is common for both equations, this means the 'a' and 'b' must also be common. </em></u>

There are two ways to find p: 'a' or 'b'

<u>a method</u>

49x^[2] = p^[2]

=> The square root of both sides = 7x = p

<u>b method</u>

28x = 4p

28x/4 = 4p/4

7x = p

6 0
2 years ago
The Diagram shows a polygon composed of rectangles
Igoryamba

To find perimeter you add up all the sides so the answer is 210

8 0
2 years ago
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mezya [45]

Answer:

4:120

Step-by-step explanation:

for 120 student they would be 4 teacher needed per 30 student

4:120

4 0
2 years ago
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