1. ## Pretty simple question

Although the topic is hard, this question is really simple...

I have to calculate Laplace transformations for L{sint}, L{cost} and, L{-cost}. I did the first two, and for the last one I got that it equals:

(-s)/(s^-1). Umm.. is this right? Is there supposed to be a negative in front of the a^2 value? (Rule from Laplace charts says L{cos(at)}= s/(s^2+a^2)..

So.. yeah, just wondering if I'm messing this problem up, i've checked my work several times, but i thought you could pull a negative sign outside of a Laplace Transform (aka L{-f(t)}= -L{f(t)})

Thanks ahead of time guys, hope this isn't a hard one

I figured it out:

For anyone who makes the same mistake as me by rare chance, you must solve for the Quantity of "-INT{e^-st*sint}". I solved for the normal int and distributed the negative into my equations so my answer was wrong.

2. Originally Posted by drewkx152
Although the topic is hard, this question is really simple...

I have to calculate Laplace transformations for L{sint}, L{cost} and, L{-cost}. I did the first two, and for the last one I got that it equals:

(-s)/(s^-1).
You mean (-s)/(s^2- 1). What you wrote is -s^2!

Umm.. is this right? Is there supposed to be a negative in front of the a^2 value? (Rule from Laplace charts says L{cos(at)}= s/(s^2+a^2)..

So.. yeah, just wondering if I'm messing this problem up, i've checked my work several times, but i thought you could pull a negative sign outside of a Laplace Transform (aka L{-f(t)}= -L{f(t)})

Thanks ahead of time guys, hope this isn't a hard one

I figured it out:

For anyone who makes the same mistake as me by rare chance, you must solve for the Quantity of "-INT{e^-st*sint}". I solved for the normal int and distributed the negative into my equations so my answer was wrong.
Yes, exactly what I was going to say!