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# c2 Integration Watch

1. Q
MS

In question 8 I chose the route of saying area of S= area below straight line - area below curve . Then I worked out both the area below curve and area below the straight line. I then I'd the subtraction. Isn't this right? This is the textbook method that I understand. In the MS they did something different which I have never seen before in my C2 book.
3. The method is good. The only difference with this is that they have taken the equation of the curve away from the equation of the line and integrated this equation to save you the hassle of finding two different areas.
4. (Original post by Coakley95)
The method is good. The only difference with this is that they have taken the equation of the curve away from the equation of the line and integrated this equation to save you the hassle of finding two different areas.
But I cannot visually understand how their method works. But I can understand my method above. I want to visually understand their method.
5. What you do is integrate equation of both the curve and the line and use the definite integral to get to different values for area. Once you have done this you take the value for the area under the curve and take it away from the area under the line. What they have done is minus the equation of the curve from the equation of the line to give you one equation to integrate. Once you integrate this equation you have already taken away the area under the curve essentially so that when you use the definite integral you get the final answer. I hope this helps.
6. (Original post by krisshP)
But I cannot visually understand how their method works. But I can understand my method above. I want to visually understand their method.
You've done

They've done

7. (Original post by tommm)
You've done

They've done

So in a general way is this right
Integral of A between limits c and v - integral of B between limit c and v

= integral of (A-B) between limits c and v
?
Thanks
8. (Original post by krisshP)
So in a general way is this right
Integral of A between limits c and v - integral of B between limit c and v

= integral of (A-B) between limits c and v
?
Thanks
Yep
9. Find the area of the area beneath the straight line and then integrate the curve between the same parameters. Take away the area from beneath the curve from the area beneath the straight line

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10. (Original post by tommm)
....
Sorry to bother you, but I was wondering if you could help me.
http://homework.king-ed.suffolk.sch....attach_id=3458

See the last question part b. They keep on changing their mark scheme method for finding the area and it's so frustrating. I used the same method in the previous paper on this question and I ended up with the correct answer . But the method for this question is different. Are examiners just looking for a correct answer with some logical working out?

Thanks
11. No it dosent matter if your meathod was to find area under both curves then minus them.As-long as you show working it should be fine.
12. (Original post by krisshP)
Are examiners just looking for a correct answer with some logical working out?
yes
13. (Original post by krisshP)
Sorry to bother you, but I was wondering if you could help me.
http://homework.king-ed.suffolk.sch....attach_id=3458

See the last question part b. They keep on changing their mark scheme method for finding the area and it's so frustrating. I used the same method in the previous paper on this question and I ended up with the correct answer . But the method for this question is different. Are examiners just looking for a correct answer with some logical working out?

Thanks
If you've managed to get the right answer with a method that makes sense, you needn't worry.
14. (Original post by TenOfThem)
yes

(Original post by tommm)
If you've managed to get the right answer with a method that makes sense, you needn't worry.
Thank you

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