learning Integration with unit step function like u(x - a)

• HanHao

  12 Sep 05, 00:35

  hello maths experts
  is the following true?
  is the graph correct?
  
  
  how about this?
  
  
  can i say that [B]u(x-a)[/B] is redundant after integration is done? can i remove it like this?
  
  i want to understand this graphically
  how would the graph of u(x-a)[F(x)-F(a)] look like compared to [F(x)-F(a)] ??
  am i correct to say that my bottom graph is [F(x)-F(a)] ??
• vincentchean

  12 Sep 05, 00:49

  3 years nv touch liao
  forgot every single thing liao
• dark_snowboy

  12 Sep 05, 00:51

  sec4 work? doesnt seem so
• Xcert

  12 Sep 05, 01:27

  Originally posted by dark_snowboy:

  sec4 work? doesnt seem so

  Nope.Uni level.
• crushedhearts

  12 Sep 05, 02:50

  u(x-a)[ F(x) - F(a)]
  
  =
  0 for xF(x) - F(a) for x>a
  
  = F(x) - F(a)
  
  ya i think it's correct...
  
  and also for
  
  b
  S f(x)u(x-a)dx ,b>a
  0
  
  simply =
  
  b
  S f(x) dx
  a
  
  ("S" for integration sign)
  hmm right?
• CoolMyth

  12 Sep 05, 08:13

  Paiseh, what is u?
• Xcert

  12 Sep 05, 11:01

  Originally posted by CoolMyth:

  Paiseh, what is u?

  u(t) is a unit step function.
  If U dunno what is a unit step function,just google it and U should have lots of results on it.