# How to evaluate this integral problem..

• Jun 3rd 2010, 07:56 PM
maiya
How to evaluate this integral problem..
How to evaluate this integration

f(x) = 2x , x<=1
f(x) - 2, x>1

$\int_{1}^{5} f(x) dx$

thanx..
• Jun 3rd 2010, 08:44 PM
mr fantastic
Quote:

Originally Posted by maiya
How to evaluate this integration

f(x) = 2x , x<=1
f(x) - 2, x>1

$\int_{1}^{5} f(x) dx$

thanx..

I suggest you first draw the graph of f(x) and then use it to see how to set up the integrals.

(Even easier of course would be to shade the area represented by the integral and use simple geometry to get the answer).
• Jun 3rd 2010, 09:29 PM
ANDS!
Quote:

Originally Posted by maiya
How to evaluate this integration

f(x) = 2x , x<=1
f(x) - 2, x>1

$\int_{1}^{5} f(x) dx$

thanx..

If your problem is written correctly, you are really only dealing with one function; look at your limits of integration - it starts off at 1, and your two functions are actually "split" at x=1. The only function that we care about is F(x)=2 (or is that -2?). This one should be pretty easy to do without even using calculus (although you should, just to show that you know how to get the right answer).
• Jun 3rd 2010, 09:46 PM
maiya
Quote:

Originally Posted by ANDS!
If your problem is written correctly, you are really only dealing with one function; look at your limits of integration - it starts off at 1, and your two functions are actually "split" at x=1. The only function that we care about is F(x)=2 (or is that -2?). This one should be pretty easy to do without even using calculus (although you should, just to show that you know how to get the right answer).

sorry, F(x)=2..

I've got the answer by drawing the graph... thanx to mr. fantastic and mr. ANDS!