Linear Algebra Examples

$[\begin{array}{c} \cos (b) & \frac{i}{g} \cdot \sin (b) \\ \sin (b) \cdot (i g) & \cos (b) \end{array}] \cdot [\begin{array}{c} \cos (a) & \frac{i}{d} \cdot \sin (a) \\ \sin (a) \cdot (i d) & \cos (a) \end{array}]$

Step 1

Combine $\frac{i}{g}$ and $\sin (b)$ .

$[\begin{array}{c} \cos (b) & \frac{i \sin (b)}{g} \\ \sin (b) \cdot (i g) & \cos (b) \end{array}] \cdot [\begin{array}{c} \cos (a) & \frac{i}{d} \cdot \sin (a) \\ \sin (a) \cdot (i d) & \cos (a) \end{array}]$

Step 2

Rewrite using the commutative property of multiplication.

$[\begin{array}{c} \cos (b) & \frac{i \sin (b)}{g} \\ i \sin (b) g & \cos (b) \end{array}] \cdot [\begin{array}{c} \cos (a) & \frac{i}{d} \cdot \sin (a) \\ \sin (a) \cdot (i d) & \cos (a) \end{array}]$

Step 3

Combine $\frac{i}{d}$ and $\sin (a)$ .

$[\begin{array}{c} \cos (b) & \frac{i \sin (b)}{g} \\ i \sin (b) g & \cos (b) \end{array}] \cdot [\begin{array}{c} \cos (a) & \frac{i \sin (a)}{d} \\ \sin (a) \cdot (i d) & \cos (a) \end{array}]$

Step 4

Rewrite using the commutative property of multiplication.

$[\begin{array}{c} \cos (b) & \frac{i \sin (b)}{g} \\ i \sin (b) g & \cos (b) \end{array}] \cdot [\begin{array}{c} \cos (a) & \frac{i \sin (a)}{d} \\ i \sin (a) d & \cos (a) \end{array}]$

Step 5

Multiply $[\begin{array}{c} \cos (b) & \frac{i \sin (b)}{g} \\ i \sin (b) g & \cos (b) \end{array}] [\begin{array}{c} \cos (a) & \frac{i \sin (a)}{d} \\ i \sin (a) d & \cos (a) \end{array}]$ .

Tap for more steps...

Step 5.1

Two matrices can be multiplied if and only if the number of columns in the first matrix is equal to the number of rows in the second matrix. In this case, the first matrix is $2 \times 2$ and the second matrix is $2 \times 2$ .

Step 5.2

Multiply each row in the first matrix by each column in the second matrix.

$[\begin{array}{c} \cos (b) \cos (a) + \frac{i \sin (b)}{g} (i \sin (a) d) & \cos (b) \frac{i \sin (a)}{d} + \frac{i \sin (b)}{g} \cos (a) \\ i \sin (b) g \cos (a) + \cos (b) (i \sin (a) d) & i \sin (b) g \frac{i \sin (a)}{d} + \cos (b) \cos (a) \end{array}]$

Step 5.3

Simplify each element of the matrix by multiplying out all the expressions.

Tap for more steps...

Step 5.3.1

Multiply $i \sin (b) g \frac{i \sin (a)}{d}$ .

Tap for more steps...

Step 5.3.1.1

Combine $i$ and $\frac{i \sin (a)}{d}$ .

$[\begin{array}{c} \cos (b) \cos (a) - \frac{d \sin (a) \sin (b)}{g} & \frac{i \cos (b) \sin (a)}{d} + \frac{i \sin (b) \cos (a)}{g} \\ i g \sin (b) \cos (a) + i d \cos (b) \sin (a) & \sin (b) g \frac{i (i \sin (a))}{d} + \cos (b) \cos (a) \end{array}]$

Step 5.3.1.2

Raise $i$ to the power of $1$ .

$[\begin{array}{c} \cos (b) \cos (a) - \frac{d \sin (a) \sin (b)}{g} & \frac{i \cos (b) \sin (a)}{d} + \frac{i \sin (b) \cos (a)}{g} \\ i g \sin (b) \cos (a) + i d \cos (b) \sin (a) & \sin (b) g \frac{i^{1} i \sin (a)}{d} + \cos (b) \cos (a) \end{array}]$

Step 5.3.1.3

Raise $i$ to the power of $1$ .

$[\begin{array}{c} \cos (b) \cos (a) - \frac{d \sin (a) \sin (b)}{g} & \frac{i \cos (b) \sin (a)}{d} + \frac{i \sin (b) \cos (a)}{g} \\ i g \sin (b) \cos (a) + i d \cos (b) \sin (a) & \sin (b) g \frac{i^{1} i^{1} \sin (a)}{d} + \cos (b) \cos (a) \end{array}]$

Step 5.3.1.4

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

$[\begin{array}{c} \cos (b) \cos (a) - \frac{d \sin (a) \sin (b)}{g} & \frac{i \cos (b) \sin (a)}{d} + \frac{i \sin (b) \cos (a)}{g} \\ i g \sin (b) \cos (a) + i d \cos (b) \sin (a) & \sin (b) g \frac{i^{1 + 1} \sin (a)}{d} + \cos (b) \cos (a) \end{array}]$

Step 5.3.1.5

Add $1$ and $1$ .

$[\begin{array}{c} \cos (b) \cos (a) - \frac{d \sin (a) \sin (b)}{g} & \frac{i \cos (b) \sin (a)}{d} + \frac{i \sin (b) \cos (a)}{g} \\ i g \sin (b) \cos (a) + i d \cos (b) \sin (a) & \sin (b) g \frac{i^{2} \sin (a)}{d} + \cos (b) \cos (a) \end{array}]$

Step 5.3.1.6

Combine $\sin (b)$ and $\frac{i^{2} \sin (a)}{d}$ .

$[\begin{array}{c} \cos (b) \cos (a) - \frac{d \sin (a) \sin (b)}{g} & \frac{i \cos (b) \sin (a)}{d} + \frac{i \sin (b) \cos (a)}{g} \\ i g \sin (b) \cos (a) + i d \cos (b) \sin (a) & g \frac{\sin (b) (i^{2} \sin (a))}{d} + \cos (b) \cos (a) \end{array}]$

Step 5.3.1.7

Combine $g$ and $\frac{\sin (b) (i^{2} \sin (a))}{d}$ .

$[\begin{array}{c} \cos (b) \cos (a) - \frac{d \sin (a) \sin (b)}{g} & \frac{i \cos (b) \sin (a)}{d} + \frac{i \sin (b) \cos (a)}{g} \\ i g \sin (b) \cos (a) + i d \cos (b) \sin (a) & \frac{g (\sin (b) (i^{2} \sin (a)))}{d} + \cos (b) \cos (a) \end{array}]$

Step 5.3.2

Simplify the numerator.

Tap for more steps...

Step 5.3.2.1

Rewrite $i^{2}$ as $- 1$ .

$[\begin{array}{c} \cos (b) \cos (a) - \frac{d \sin (a) \sin (b)}{g} & \frac{i \cos (b) \sin (a)}{d} + \frac{i \sin (b) \cos (a)}{g} \\ i g \sin (b) \cos (a) + i d \cos (b) \sin (a) & \frac{g \sin (b) \cdot - 1 \sin (a)}{d} + \cos (b) \cos (a) \end{array}]$

Step 5.3.2.2

Factor out negative.

$[\begin{array}{c} \cos (b) \cos (a) - \frac{d \sin (a) \sin (b)}{g} & \frac{i \cos (b) \sin (a)}{d} + \frac{i \sin (b) \cos (a)}{g} \\ i g \sin (b) \cos (a) + i d \cos (b) \sin (a) & \frac{- g \sin (b) \sin (a)}{d} + \cos (b) \cos (a) \end{array}]$

Step 5.3.3

Move the negative in front of the fraction.

$[\begin{array}{c} \cos (b) \cos (a) - \frac{d \sin (a) \sin (b)}{g} & \frac{i \cos (b) \sin (a)}{d} + \frac{i \sin (b) \cos (a)}{g} \\ i g \sin (b) \cos (a) + i d \cos (b) \sin (a) & - \frac{g \sin (b) \sin (a)}{d} + \cos (b) \cos (a) \end{array}]$