Precalculus Examples

$20 \sum_{x = 0}^{3} | \sin (2.8 π x) \cdot \sin (3.48 π x) |$

Step 1

Simplify the summation.

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Step 1.1

Multiply $2.8$ by $π$ .

$| \sin (8.79645943 x) \cdot \sin (3.48 π x) |$

Step 1.2

Multiply $3.48$ by $π$ .

$| \sin (8.79645943 x) \sin (10.93274243 x) |$

Step 1.3

Rewrite the summation.

$20 \sum_{x = 0}^{3} | \sin (8.79645943 x) \sin (10.93274243 x) |$

Step 2

Expand the series for each value of $x$ .

$20 (| \sin (8.79645943 \cdot 0) \sin (10.93274243 \cdot 0) | + | \sin (8.79645943 \cdot 1) \sin (10.93274243 \cdot 1) | + | \sin (8.79645943 \cdot 2) \sin (10.93274243 \cdot 2) | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3

Simplify.

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Step 3.1

Evaluate $\sin (8.79645943 \cdot 0)$ .

$20 (| 0 \sin (10.93274243 \cdot 0) | + | \sin (8.79645943 \cdot 1) \sin (10.93274243 \cdot 1) | + | \sin (8.79645943 \cdot 2) \sin (10.93274243 \cdot 2) | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.2

Evaluate $\sin (10.93274243 \cdot 0)$ .

$20 (| 0 \cdot 0 | + | \sin (8.79645943 \cdot 1) \sin (10.93274243 \cdot 1) | + | \sin (8.79645943 \cdot 2) \sin (10.93274243 \cdot 2) | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.3

Multiply $0$ by $0$ .

$20 (| 0 | + | \sin (8.79645943 \cdot 1) \sin (10.93274243 \cdot 1) | + | \sin (8.79645943 \cdot 2) \sin (10.93274243 \cdot 2) | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.4

The absolute value is the distance between a number and zero. The distance between $0$ and $0$ is $0$ .

$20 (0 + | \sin (8.79645943 \cdot 1) \sin (10.93274243 \cdot 1) | + | \sin (8.79645943 \cdot 2) \sin (10.93274243 \cdot 2) | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.5

Evaluate $\sin (8.79645943 \cdot 1)$ .

$20 (0 + | 0.58778525 \sin (10.93274243 \cdot 1) | + | \sin (8.79645943 \cdot 2) \sin (10.93274243 \cdot 2) | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.6

Evaluate $\sin (10.93274243 \cdot 1)$ .

$20 (0 + | 0.58778525 \cdot 0.18965656 | + | \sin (8.79645943 \cdot 2) \sin (10.93274243 \cdot 2) | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.7

Multiply $0.58778525$ by $0.18965656$ .

$20 (0 + | 0.11147733 | + | \sin (8.79645943 \cdot 2) \sin (10.93274243 \cdot 2) | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.8

The absolute value is the distance between a number and zero. The distance between $0$ and $0.11147733$ is $0.11147733$ .

$20 (0 + 0.11147733 + | \sin (8.79645943 \cdot 2) \sin (10.93274243 \cdot 2) | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.9

Add $0$ and $0.11147733$ .

$20 (0.11147733 + | \sin (8.79645943 \cdot 2) \sin (10.93274243 \cdot 2) | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.10

Evaluate $\sin (8.79645943 \cdot 2)$ .

$20 (0.11147733 + | 0.30225208 \sin (10.93274243 \cdot 2) | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.11

Evaluate $\sin (10.93274243 \cdot 2)$ .

$20 (0.11147733 + | 0.30225208 \cdot 0.37242878 | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.12

Multiply $0.30225208$ by $0.37242878$ .

$20 (0.11147733 + | 0.11256737 | + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.13

The absolute value is the distance between a number and zero. The distance between $0$ and $0.11256737$ is $0.11256737$ .

$20 (0.11147733 + 0.11256737 + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.14

Add $0.11147733$ and $0.11256737$ .

$20 (0.2240447 + | \sin (8.79645943 \cdot 3) \sin (10.93274243 \cdot 3) |)$

Step 3.15

Evaluate $\sin (8.79645943 \cdot 3)$ .

$20 (0.2240447 + | 0.44446912 \sin (10.93274243 \cdot 3) |)$

Step 3.16

Evaluate $\sin (10.93274243 \cdot 3)$ .

$20 (0.2240447 + | 0.44446912 \cdot 0.5416822 |)$

Step 3.17

Multiply $0.44446912$ by $0.5416822$ .

$20 (0.2240447 + | 0.24076101 |)$

Step 3.18

The absolute value is the distance between a number and zero. The distance between $0$ and $0.24076101$ is $0.24076101$ .

$20 (0.2240447 + 0.24076101)$

Step 3.19

Add $0.2240447$ and $0.24076101$ .

$20 \cdot 0.46480572$

Step 3.20

Multiply $20$ by $0.46480572$ .

$9.29611442$