Matrices Flashcards

1
Q

A matrix has dimensions 2 x 3.
What does this mean?

A

It has 2 rows and 3 columns

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2
Q

When can you add and subtract matrices?

A

When they have the same dimensions

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3
Q

What is ((A^-1)(B^-1))^-1

A

BA

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4
Q

When can you multiply two matrices : A x B

A

When the columns of A = the rows of B

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5
Q

What are the dimensions of C:
A x B = C

A

Dimensions: the rows of A x the columns of B

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6
Q

Give the 3x3 matrix corresponding to a reflection in the y=0 plane

A

1 0 0
0 -1 0
0 0 1

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7
Q

Give the 3x3 matrix corresponding to a reflection in the x=0 plane

A

-1 0 0
0 1 0
0 0 1

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8
Q

Give the 3x3 matrix corresponding to a reflection in the xy plane

A

xy plane <=> z=0 plane

1 0 0
0 1 0
0 0 1

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9
Q

What is the inverse of the 2x2 matrix:

a b
c d

A

d -b
-c b

then divide by the determinant (formatting this is hard)

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