Linear Algebra Examples

$[\begin{array}{c} e^{x} & \cos (x) & \sin (x) \\ e^{x} & - \sin (x) & \cos (x) \\ e^{x} & - \cos (x) & - \sin (x) \end{array}]$

Step 1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} - \sin (x) & \cos (x) \\ - \cos (x) & - \sin (x) \end{array} |$

Step 1.4

Multiply element $a_{11}$ by its cofactor.

$e^{x} | \begin{array}{c} - \sin (x) & \cos (x) \\ - \cos (x) & - \sin (x) \end{array} |$

Step 1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} |$

Step 1.6

Multiply element $a_{12}$ by its cofactor.

$- \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} |$

Step 1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 1.8

Multiply element $a_{13}$ by its cofactor.

$\sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 1.9

Add the terms together.

$e^{x} | \begin{array}{c} - \sin (x) & \cos (x) \\ - \cos (x) & - \sin (x) \end{array} | - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2

Evaluate $| \begin{array}{c} - \sin (x) & \cos (x) \\ - \cos (x) & - \sin (x) \end{array} |$ .

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Step 2.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$e^{x} (- \sin (x) (- \sin (x)) - (- \cos (x) \cos (x))) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2

Simplify the determinant.

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Step 2.2.1

Simplify each term.

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Step 2.2.1.1

Multiply $- \sin (x) (- \sin (x))$ .

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Step 2.2.1.1.1

Multiply $- 1$ by $- 1$ .

$e^{x} (1 \sin (x) \sin (x) - (- \cos (x) \cos (x))) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.1.1.2

Multiply $\sin (x)$ by $1$ .

$e^{x} (\sin (x) \sin (x) - (- \cos (x) \cos (x))) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.1.1.3

Raise $\sin (x)$ to the power of $1$ .

$e^{x} (\sin^{1} (x) \sin (x) - (- \cos (x) \cos (x))) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.1.1.4

Raise $\sin (x)$ to the power of $1$ .

$e^{x} (\sin^{1} (x) \sin^{1} (x) - (- \cos (x) \cos (x))) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.1.1.5

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$e^{x} ({\sin (x)}^{1 + 1} - (- \cos (x) \cos (x))) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.1.1.6

Add $1$ and $1$ .

$e^{x} (\sin^{2} (x) - (- \cos (x) \cos (x))) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.1.2

Multiply $- \cos (x) \cos (x)$ .

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Step 2.2.1.2.1

Raise $\cos (x)$ to the power of $1$ .

$e^{x} (\sin^{2} (x) - - (\cos^{1} (x) \cos (x))) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.1.2.2

Raise $\cos (x)$ to the power of $1$ .

$e^{x} (\sin^{2} (x) - - (\cos^{1} (x) \cos^{1} (x))) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.1.2.3

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$e^{x} (\sin^{2} (x) - - {\cos (x)}^{1 + 1}) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.1.2.4

Add $1$ and $1$ .

$e^{x} (\sin^{2} (x) - - \cos^{2} (x)) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.1.3

Multiply $- - \cos^{2} (x)$ .

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Step 2.2.1.3.1

Multiply $- 1$ by $- 1$ .

$e^{x} (\sin^{2} (x) + 1 \cos^{2} (x)) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.1.3.2

Multiply $\cos^{2} (x)$ by $1$ .

$e^{x} (\sin^{2} (x) + \cos^{2} (x)) - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 2.2.2

Apply pythagorean identity.

$e^{x} \cdot 1 - \cos (x) | \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} | + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 3

Evaluate $| \begin{array}{c} e^{x} & \cos (x) \\ e^{x} & - \sin (x) \end{array} |$ .

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Step 3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$e^{x} \cdot 1 - \cos (x) (e^{x} (- \sin (x)) - e^{x} \cos (x)) + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 3.2

Rewrite using the commutative property of multiplication.

$e^{x} \cdot 1 - \cos (x) (- e^{x} \sin (x) - e^{x} \cos (x)) + \sin (x) | \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$

Step 4

Evaluate $| \begin{array}{c} e^{x} & - \sin (x) \\ e^{x} & - \cos (x) \end{array} |$ .

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Step 4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$e^{x} \cdot 1 - \cos (x) (- e^{x} \sin (x) - e^{x} \cos (x)) + \sin (x) (e^{x} (- \cos (x)) - e^{x} (- \sin (x)))$

Step 4.2

Simplify each term.

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Step 4.2.1

Rewrite using the commutative property of multiplication.

$e^{x} \cdot 1 - \cos (x) (- e^{x} \sin (x) - e^{x} \cos (x)) + \sin (x) (- e^{x} \cos (x) - e^{x} (- \sin (x)))$

Step 4.2.2

Multiply $- e^{x} (- \sin (x))$ .

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Step 4.2.2.1

Multiply $- 1$ by $- 1$ .

$e^{x} \cdot 1 - \cos (x) (- e^{x} \sin (x) - e^{x} \cos (x)) + \sin (x) (- e^{x} \cos (x) + 1 e^{x} \sin (x))$

Step 4.2.2.2

Multiply $e^{x}$ by $1$ .

$e^{x} \cdot 1 - \cos (x) (- e^{x} \sin (x) - e^{x} \cos (x)) + \sin (x) (- e^{x} \cos (x) + e^{x} \sin (x))$

Step 5

Simplify the determinant.

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Step 5.1

Simplify each term.

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Step 5.1.1

Multiply $e^{x}$ by $1$ .

$e^{x} - \cos (x) (- e^{x} \sin (x) - e^{x} \cos (x)) + \sin (x) (- e^{x} \cos (x) + e^{x} \sin (x))$

Step 5.1.2

Apply the distributive property.

$e^{x} - \cos (x) (- e^{x} \sin (x)) - \cos (x) (- e^{x} \cos (x)) + \sin (x) (- e^{x} \cos (x) + e^{x} \sin (x))$

Step 5.1.3

Multiply $- \cos (x) (- e^{x} \sin (x))$ .

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Step 5.1.3.1

Multiply $- 1$ by $- 1$ .

$e^{x} + 1 \cos (x) (e^{x} \sin (x)) - \cos (x) (- e^{x} \cos (x)) + \sin (x) (- e^{x} \cos (x) + e^{x} \sin (x))$

Step 5.1.3.2

Multiply $\cos (x)$ by $1$ .

$e^{x} + \cos (x) (e^{x} \sin (x)) - \cos (x) (- e^{x} \cos (x)) + \sin (x) (- e^{x} \cos (x) + e^{x} \sin (x))$

Step 5.1.4

Multiply $- \cos (x) (- e^{x} \cos (x))$ .

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Step 5.1.4.1

Multiply $- 1$ by $- 1$ .

$e^{x} + \cos (x) (e^{x} \sin (x)) + 1 \cos (x) (e^{x} \cos (x)) + \sin (x) (- e^{x} \cos (x) + e^{x} \sin (x))$

Step 5.1.4.2

Multiply $\cos (x)$ by $1$ .

$e^{x} + \cos (x) (e^{x} \sin (x)) + \cos (x) (e^{x} \cos (x)) + \sin (x) (- e^{x} \cos (x) + e^{x} \sin (x))$

Step 5.1.4.3

Raise $\cos (x)$ to the power of $1$ .

$e^{x} + \cos (x) (e^{x} \sin (x)) + \cos^{1} (x) \cos (x) e^{x} + \sin (x) (- e^{x} \cos (x) + e^{x} \sin (x))$

Step 5.1.4.4

Raise $\cos (x)$ to the power of $1$ .

$e^{x} + \cos (x) (e^{x} \sin (x)) + \cos^{1} (x) \cos^{1} (x) e^{x} + \sin (x) (- e^{x} \cos (x) + e^{x} \sin (x))$

Step 5.1.4.5

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$e^{x} + \cos (x) (e^{x} \sin (x)) + {\cos (x)}^{1 + 1} e^{x} + \sin (x) (- e^{x} \cos (x) + e^{x} \sin (x))$

Step 5.1.4.6

Add $1$ and $1$ .

$e^{x} + \cos (x) (e^{x} \sin (x)) + \cos^{2} (x) e^{x} + \sin (x) (- e^{x} \cos (x) + e^{x} \sin (x))$

Step 5.1.5

Apply the distributive property.

$e^{x} + \cos (x) e^{x} \sin (x) + \cos^{2} (x) e^{x} + \sin (x) (- e^{x} \cos (x)) + \sin (x) (e^{x} \sin (x))$

Step 5.1.6

Rewrite using the commutative property of multiplication.

$e^{x} + \cos (x) e^{x} \sin (x) + \cos^{2} (x) e^{x} - \sin (x) e^{x} \cos (x) + \sin (x) (e^{x} \sin (x))$

Step 5.1.7

Multiply $\sin (x) (e^{x} \sin (x))$ .

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Step 5.1.7.1

Raise $\sin (x)$ to the power of $1$ .

$e^{x} + \cos (x) e^{x} \sin (x) + \cos^{2} (x) e^{x} - \sin (x) e^{x} \cos (x) + \sin^{1} (x) \sin (x) e^{x}$

Step 5.1.7.2

Raise $\sin (x)$ to the power of $1$ .

$e^{x} + \cos (x) e^{x} \sin (x) + \cos^{2} (x) e^{x} - \sin (x) e^{x} \cos (x) + \sin^{1} (x) \sin^{1} (x) e^{x}$

Step 5.1.7.3

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$e^{x} + \cos (x) e^{x} \sin (x) + \cos^{2} (x) e^{x} - \sin (x) e^{x} \cos (x) + {\sin (x)}^{1 + 1} e^{x}$

Step 5.1.7.4

Add $1$ and $1$ .

$e^{x} + \cos (x) e^{x} \sin (x) + \cos^{2} (x) e^{x} - \sin (x) e^{x} \cos (x) + \sin^{2} (x) e^{x}$

Step 5.2

Combine the opposite terms in $e^{x} + \cos (x) e^{x} \sin (x) + \cos^{2} (x) e^{x} - \sin (x) e^{x} \cos (x) + \sin^{2} (x) e^{x}$ .

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Step 5.2.1

Reorder the factors in the terms $\cos (x) e^{x} \sin (x)$ and $- \sin (x) e^{x} \cos (x)$ .

$e^{x} + e^{x} \cos (x) \sin (x) + \cos^{2} (x) e^{x} - e^{x} \cos (x) \sin (x) + \sin^{2} (x) e^{x}$

Step 5.2.2

Subtract $e^{x} \cos (x) \sin (x)$ from $e^{x} \cos (x) \sin (x)$ .

$e^{x} + \cos^{2} (x) e^{x} + 0 + \sin^{2} (x) e^{x}$

Step 5.2.3

Add $e^{x} + \cos^{2} (x) e^{x}$ and $0$ .

$e^{x} + \cos^{2} (x) e^{x} + \sin^{2} (x) e^{x}$

Step 5.3

Factor $e^{x}$ out of $e^{x} + \cos^{2} (x) e^{x} + \sin^{2} (x) e^{x}$ .

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Step 5.3.1

Multiply by $1$ .

$e^{x} \cdot 1 + \cos^{2} (x) e^{x} + \sin^{2} (x) e^{x}$

Step 5.3.2

Factor $e^{x}$ out of $\cos^{2} (x) e^{x}$ .

$e^{x} \cdot 1 + e^{x} \cos^{2} (x) + \sin^{2} (x) e^{x}$

Step 5.3.3

Factor $e^{x}$ out of $\sin^{2} (x) e^{x}$ .

$e^{x} \cdot 1 + e^{x} \cos^{2} (x) + e^{x} \sin^{2} (x)$

Step 5.3.4

Factor $e^{x}$ out of $e^{x} \cdot 1 + e^{x} \cos^{2} (x)$ .

$e^{x} \cdot (1 + \cos^{2} (x)) + e^{x} \sin^{2} (x)$

Step 5.3.5

Factor $e^{x}$ out of $e^{x} \cdot (1 + \cos^{2} (x)) + e^{x} \sin^{2} (x)$ .

$e^{x} (1 + \cos^{2} (x) + \sin^{2} (x))$

Step 5.4

Rearrange terms.

$e^{x} (1 + \sin^{2} (x) + \cos^{2} (x))$

Step 5.5

Apply pythagorean identity.

$e^{x} (1 + 1)$

Step 5.6

Add $1$ and $1$ .

$e^{x} \cdot 2$

Step 5.7

Move $2$ to the left of $e^{x}$ .

$2 e^{x}$