Maths Enquiry

S

shermaine

New Member

• Oct 10, 2004

• #1

Hello,

May i know how to integrate this 2 x integrate exp(-2t)dt?
Why is the answer is 1? Please advise. Thanks.

 

Styx

Active Member

• Oct 10, 2004

• #2

2*Int(exp(-2t))dt = -1/(2*exp(t)^2 + C

an integral can only equal one IF it is perfomed with integration limits. THe result of an integration is always a function of the integration operand

 

jrz126

Active Member

• Oct 10, 2004

• #3

wouldnt it be -exp(-2t) + C? the term inside the exp doesnt change.
(I plugged it into my calculator, and thats what it gave me)

 

Styx

Active Member

• Oct 10, 2004

• #4

oh yer did a mistake on that 1

 

electronist

New Member

• Oct 11, 2004

• #5

integrate exp(-2t) = -1/2(exp(-2t))
and since 2 in Nr, and Dr divide out the final outcome is
- (exp(-2t))
May be if you want the ans to be 1 you can write
-(exp(-2t)) = 1 and find the value for t hence getting the limits of integration. i suppose t = - infinity, OR simply 1 cannot be the answer
Here initial value again is not taken into account
I guess i repeated all the above suggestions

 

S

shermaine

New Member

• Oct 11, 2004

• #6

Hi all,

The Q is something like this.

Determine the energy and power of the signal y(t) = exp (-t).
Check if this function is a energy or power type.
Please advise. Thanks.

 

plot

New Member

• Oct 11, 2004

• #7

e^0 = 1

so at t = 0, the function will equal 1.

 

Styx

Active Member

• Oct 11, 2004

• #8

plot said:

e^0 = 1

so at t = 0, the function will equal 1.

Click to expand...

except that it is an integration and MUST be over a time range.

that function should equal 0 at t=Inf so an integration boundary of t=0 to t=inf will give you a value of 1