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4 years ago

Which expression calculates the time in hours an object takes to travel 38 miles at a speed of 2 m/hm/h ?

Mathematics

1 answer:

yaroslaw [1]4 years ago

4 0

38/2 is 19
38-238-2= -202
38+238+2= 278

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Given: PRbisects ZQPS, PQ = 12units, and PS= 12units

Ganezh [65]

Answer:

Use SAS to show that triangles PRQ and PRS are congruent.

Step-by-step explanation:

Since PR bisects angle QPS, angles QPR and SPR are congruent. By reflexive property of congruence, PR is congruent to itself. Since PQ is congruent to PS, we can use SAS to show that the two triangles are congruent. By CPCTC, QR is congruent to SR.

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3 years ago

There are 16 cups in a gallon. The equation c=16g gives the number of cups in terms of the number of gallons. Write another equa

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3 years ago

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Brianna's teacher asks her which of these three expressions are equivalent to each other.

jekas [21]

Brianna's thinking is incorrect.
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4 years ago

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Find a formula for the least squares solution of ax=b when the columns of a are orthonormal1 .

neonofarm [45]

Let $\mathbf A$ be a rectangular $m\times n$ matrix with column vectors $\mathbf a_1,\ldots,\mathbf a_n$ , i.e.

$\mathbf A=\begin{bmatrix}\mathbf a_1&\cdots&\mathbf a_n\end{bmatrix}$

Then we have

$\mathbf A^\top=\begin{bmatrix}\mathbf a_1&\cdots&\mathbf a_n\end{bmatrix}^\top$

and the product of the two is

$\mathbf A^\top\mathbf A=\begin{bmatrix}\mathbf a_1\cdot\mathbf a_1&\mathbf a_1\cdot\mathbf a_2&\cdots&\mathbf a_1\cdot\mathbf a_n\\\mathbf a_2\cdot\mathbf a_1&\mathbf a_2\cdot\mathbf a_2&\cdots&\mathbf a_2\cdot\mathbf a_n\\\vdots&\vdots&\ddots&\vdots\\\mathbf a_n\cdot\mathbf a_1&\mathbf a_n\cdot\mathbf a_2&\cdots&\mathbf a_n\cdot\mathbf a_n\end{bmatrix}$

Because the columns of $\mathbf A$ are orthonormal, we have

$\mathbf a_i\cdot\mathbf a_j=\begin{cases}1&\text{for }i=j\\0&\text{for }i\neq j\end{cases}$

which means $\mathbf A^\top\mathbf A$ reduces to an $n\times n$ matrix with ones along the diagonal and zero everywhere else, i.e.

$\mathbf A^\top\mathbf A=\begin{bmatrix}1&0&\cdots&0\\0&1&\cdots&0\\\vdots&\vdots&\ddots&\vdots\\0&0&\cdots&1\end{bmatrix}=\mathbf I_n$

where $\mathbf I$ denotes the identity matrix. This means the solution to $\mathbf{Ax}=\mathbf b$ is given by

$\mathbf A^\top(\mathbf{Ax})=\mathbf A^\top\mathbf b\implies(\underbrace{\mathbf A^\top\mathbf A}_{\mathbf I})\mathbf x=\mathbf A^\top\mathbf b\implies\mathbf x=\mathbf A^\top\mathbf b$

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3 years ago