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# C2 Trapezium rule and logs easy questions

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1. Trapezium rule:

For a) I know the height is 0.5, but using the formula h = (b-a)/n I don't get 0.5, I use b as 4 and a as 1 and n as 7, but obviously n has to be 6, thought i see 7 intervals. Is it because the last interval is 0?

Logs question:

For part bii) I got the question correct, but I done a complete different method from the mark scheme, and I'm wondering how the mark scheme did it.

My method:

This is correct, but the mark scheme simply got:

If anyone could explain how they got this would be great.
2. (Original post by thorn0123)
Trapezium rule:

For a) I know the height is 0.5, but using the formula h = (b-a)/n I don't get 0.5, I use b as 4 and a as 1 and n as 7, but obviously n has to be 6, thought i see 7 intervals. Is it because the last interval is 0?

Logs question:

For part bii) I got the question correct, but I done a complete different method from the mark scheme, and I'm wondering how the mark scheme did it.

My method:

This is correct, but the mark scheme simply got:

If anyone could explain how they got this would be great.

I'll look into the trapezium rule question if it's not answered yet when I have more time. Most likely it will though, answers come fast in this forum.
3. (Original post by thorn0123)
Trapezium rule:

For a) I know the height is 0.5, but using the formula h = (b-a)/n I don't get 0.5, I use b as 4 and a as 1 and n as 7, but obviously n has to be 6, thought i see 7 intervals. Is it because the last interval is 0?

Logs question:

For part bii) I got the question correct, but I done a complete different method from the mark scheme, and I'm wondering how the mark scheme did it.

My method:

This is correct, but the mark scheme simply got:

If anyone could explain how they got this would be great.
Multiply everything through by log 5 to get rid of the fraction.
4. 1-((log2/log5)) = 1/x

(log5/log5)=1

(log5-log2)/log5 =1/x

flip it round to find x (reciprocal)

log5/(log5-log2) = x

It's just neater to write this way than yours.

For trapezium rule question.
b=4 a=1 n=6 (because there are 6 strips and 7 ordinates) there are always one more ordinate than strips, try drawing it out with 6 strips and you'll see what I mean.
5. Ok I understand the log question, but what is an ordinate? I've drawn 6 strips and I still don't see what you mean.
6. (Original post by thorn0123)
Ok I understand the log question, but what is an ordinate? I've drawn 6 strips and I still don't see what you mean.
An ordinate is like a point, there is always one more than the number of strips when using the trapezium rule.

Edit If you still don't get it
Spoiler:
Show
Ordinates = 7 therefore 6 strips.

Using

7. the x values are what I meant, so you have 1,1.5,2 to 4.
7 values (ordinates there)
8. thanks
9. are these from edexcel papers?

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