c2 integration (look at attachment)

Integrate from 0 to 3, make it positive, and add it to the integral from 3 to 5.

Reply 2

Original post by freedomhunter

I have attached a question that im slightly confuzzled about. Part i I can do, but if someone should just explain how to do ii :s-smilie:

Thanks a lot

I literally did this question 10 minutes ago. When you integrate form 0-5 you are evaluating. The reason it will be less than the total area is because integrating between 0-3 will give a negative value.

To get the answer, which is 79/6, you must integrate between 0-3 and 3-5 (separately) and then subtract your integration between 0-3 form your integration between 3-5.

Reply 3

Original post by meatball893

Integrate from 0 to 3, make it positive, and add it to the integral from 3 to 5.

Why would u make it positve :s-smilie:

Reply 4

Original post by Killjoy-

...then subtract your integration between 0-3 form your integration between 3-5.

this is the ony bit i dont get it :s-smilie:

why do you do that :s-smilie:

Reply 5

Original post by freedomhunter

this is the ony bit i dont get it :s-smilie:

why do you do that :s-smilie:

Because 0-3 will be negative, so you have to account for it by 'making it positive.' That way you are finding the total area, and not just evaluating.

Reply 6

Original post by freedomhunter

Why would u make it positve :s-smilie:

You want the total area. But integrating from 0 to 3 will give you a negative area, which you don't want. It'll have the right value, but the wrong sign. So change the sign.

What is your answer to i)?

Reply 7

Thanks guys - i get it now! (I cant rep you anymore because ive run out of reps:P)

answer to part i) is because some of the area is under the x-axis

Reply 8

Original post by freedomhunter

Thanks guys - i get it now! (I cant rep you anymore because ive run out of reps:P)

answer to part i) is because some of the area is under the x-axis

You may want to explain why that matters. But I'm glad you get (ii) now :biggrin:

Reply 9

Original post by freedomhunter

Thanks guys - i get it now! (I cant rep you anymore because ive run out of reps:P)

answer to part i) is because some of the area is under the x-axis

Good Luck for your exam :smile:

I have it today as well.

Reply 10

Original post by meatball893

You may want to explain why that matters. But I'm glad you get (ii) now :biggrin:

How would you explain why it matters? what would you say..

Reply 11

Original post by Killjoy-

Good Luck for your exam :smile:

I have it today as well.

how you feeling for the exam? What prep have you done so far?

Reply 12

Killjoy-

freedomhunter

Your exam is today? Wow, hope it goes well!

Reply 13

Original post by freedomhunter

how you feeling for the exam? What prep have you done so far?

I've gone through almost all the papers twice now. I understand the content, but even with this I keep making stupid mistakes so I loose at least a few marks.

Compared to other exams though, I'm feeling okay (Haven't said that for a while).

Reply 14

Original post by meatball893

Your exam is today? Wow, hope it goes well!

Thank you! And well done for your A2 grades by the way!

Reply 15

JongKey

Yeah like others have said

1. Integrate 5-3, 3-0 separately
2. Make the 3-0 part positive
3. Add the two parts together

26/3 + 9/2 = 13 1/6 or 79/6

Reply 16