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Linear Algebra: Orthogonal Columns
Let 
M be





1
3
1


2
-2

a


1
1

b




and tet 
a and 
b be such that the columns of 
M are orthogonat. Compute 
a
Pick ONE option

-1//2

-1

1//2
2
Ciear Selection

77. Linear Algebra: Orthogonal Columns\newlineLet M M be\newline\begin{tabular}{|l|l|l|}\newline\hline 11 & 33 & 11 \\\newline\hline 22 & 2-2 & a a \\\newline\hline 11 & 11 & b b \\\newline\hline\newline\end{tabular}\newlineand tet a \mathrm{a} and b \mathrm{b} be such that the columns of M \mathrm{M} are orthogonat. Compute a \mathrm{a} \newlinePick ONE option\newline1/2 -1 / 2 \newline1 -1 \newline1/2 1 / 2 \newline22\newlineCiear Selection

Full solution

Q. 77. Linear Algebra: Orthogonal Columns\newlineLet M M be\newline\begin{tabular}{|l|l|l|}\newline\hline 11 & 33 & 11 \\\newline\hline 22 & 2-2 & a a \\\newline\hline 11 & 11 & b b \\\newline\hline\newline\end{tabular}\newlineand tet a \mathrm{a} and b \mathrm{b} be such that the columns of M \mathrm{M} are orthogonat. Compute a \mathrm{a} \newlinePick ONE option\newline1/2 -1 / 2 \newline1 -1 \newline1/2 1 / 2 \newline22\newlineCiear Selection
  1. Determine value of aa: To determine the value of aa, we need to ensure that the dot product of the first and second columns of matrix MM is zero, since orthogonal columns have a dot product of zero.\newlineThe first column of MM is [1,2,1][1, 2, 1] and the second column is [3,2,a][3, -2, a].\newlineThe dot product of these two columns is calculated as follows:\newline(1×3)+(2×2)+(1×a)=0(1 \times 3) + (2 \times -2) + (1 \times a) = 0\newline34+a=03 - 4 + a = 0\newlinea=1a = 1
  2. Calculate dot product: Now, we need to check if the third column [1,b][1, b] is orthogonal to the other two columns. Since we only have a value for aa and not for bb, we can only check the orthogonality with respect to aa. The dot product of the first and third columns is: (1×1)+(2×b)+(1×1)=0(1 \times 1) + (2 \times b) + (1 \times 1) = 0 1+2b+1=01 + 2b + 1 = 0 2b=22b = -2 b=1b = -1
  3. Check orthogonality: However, we made a mistake in the previous step. We were only asked to compute aa, not bb. Therefore, we should not have calculated the value of bb. We will disregard the previous step's calculation for bb and focus on the value of aa that we found.

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