Math  /  Calculus

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Standard 16: Problem 6 (1 point)
Find the Laplace transform of 5cos(at)2emt5 \cos (a t)-2 e^{m t} : \square
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Studdy Solution

STEP 1

What is this asking? We need to find the Laplace transform of the expression 5cos(at)2emt5 \cos(at) - 2e^{mt}. Watch out! Remember the specific formulas for the Laplace transforms of cosine and exponential functions!
Don't mix them up.

STEP 2

1. Laplace Transform of Cosine
2. Laplace Transform of Exponential
3. Combine the Results

STEP 3

Let's **start** with the Laplace transform of 5cos(at)5 \cos(at).
Remember, the Laplace transform of cos(at)\cos(at) is given by ss2+a2\frac{s}{s^2 + a^2}.
So, we're going to use that!

STEP 4

Now, we **multiply** that by **5** to get the Laplace transform of 5cos(at)5 \cos(at), which is 5ss2+a2=5ss2+a25 \cdot \frac{s}{s^2 + a^2} = \frac{5s}{s^2 + a^2}.
See? Not so bad!

STEP 5

Next up is the Laplace transform of 2emt-2e^{mt}.
The Laplace transform of emte^{mt} is 1sm\frac{1}{s - m}.
Keep this formula in mind, it's a good one!

STEP 6

We **multiply** by 2-2 to find the Laplace transform of 2emt-2e^{mt}, which gives us 21sm=2sm-2 \cdot \frac{1}{s - m} = \frac{-2}{s - m}.
Awesome!

STEP 7

Finally, we **put it all together**.
Since the Laplace transform is a linear operator, we can just add the individual transforms we found.

STEP 8

The Laplace transform of 5cos(at)2emt5 \cos(at) - 2e^{mt} is the **sum** of the transforms we calculated: 5ss2+a2+2sm\frac{5s}{s^2 + a^2} + \frac{-2}{s - m}.
We can rewrite this as 5ss2+a22sm\frac{5s}{s^2 + a^2} - \frac{2}{s - m}.

STEP 9

The Laplace transform of 5cos(at)2emt5 \cos(at) - 2e^{mt} is 5ss2+a22sm\frac{5s}{s^2 + a^2} - \frac{2}{s - m}.

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