# simple integration

• Mar 21st 2010, 09:21 AM
alexandrabel90
simple integration
given that f(y1,y2) = exp (-(y1+y2)) where y1 and y2 are greater than 0. find P(Y1<1, Y2>5)..

i know that i need to use the double integral but im unable to determine the range that i should integrate it under..can someone please teach me a method where i can find out the range?

thanks
• Mar 22nd 2010, 12:23 AM
CaptainBlack
Quote:

Originally Posted by alexandrabel90
given that f(y1,y2) = exp (-(y1+y2)) where y1 and y2 are greater than 0. find P(Y1<1, Y2>5)..

i know that i need to use the double integral but im unable to determine the range that i should integrate it under..can someone please teach me a method where i can find out the range?

thanks

$P(Y_1<1, Y_2>5)=\int_{y_1=0}^1 \int_{y_2=5}^{\infty} f_{Y_1,Y_2}(y_1,y_2)\; dy_2 dy_1$

CB
• Mar 22nd 2010, 03:49 AM
mr fantastic
Quote:

Originally Posted by alexandrabel90
given that f(y1,y2) = exp (-(y1+y2)) where y1 and y2 are greater than 0. find P(Y1<1, Y2>5)..

i know that i need to use the double integral but im unable to determine the range that i should integrate it under..can someone please teach me a method where i can find out the range?

thanks

But you said in another thread that you have studied double integration. You need to go back and thoroughly review that material because all these types of questions depend on it.
• Mar 22nd 2010, 03:59 AM
alexandrabel90
ok. im currently studying it down under calculus and stats o im still pretty unfamiliar with how double integrals work. i guess i need more practise on them.
thanks!