Question

find the laplace transform of tcos(2t)

Answer 1

do u know the L.T of cos 2t ?

Answer 2

yes so its s/(s^2 + 4)

Answer 3

so do i have to take the integral of the function first? or...

Answer 4

now u need to use
\(\large L[t^nf(t)]=(-1)^n\frac{d^n}{ds^n}[F(s)]\)
did u know this ?

Answer 5

no i dont take the integral theres got to be an easier way

Answer 6

okay but then what is F(s) in this case?

Answer 7

F(s) is the Laplace transfom of f(t)
in this case, f(t) is cos 2t
and F(s) is its L.T

Answer 8

so it would be -1 * d/ds * F(s)

Answer 9

thats why i first asked whether u know L.T of cos 2t

Answer 10

YUP

Answer 11

wait so why isnt f(t) tcos(2t) and is cos(2t) haha

Answer 12

because t^1 is multiplied by cos 2t
so, according to
t^n f(t)
f(t) is cos 2t and n=1

Answer 13

oh my gosh thats why im messing up thank you so much hartnn :)

Answer 14

welcome ^_^
i hope you can finish now....

Answer 15

got it!:) thanks again