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# P2 Trapezium Rule watch

1. Question four on the mock paper (edexcel) includes the following;

b) sketch the curve with the following equation; y=sec x, -pi/3 < x < pi/3

sketched and sketched correctly, then...

using the trapezium rule with five evenly spaced ordinates to estimate the area of the region bounded by the curve with the equation y=sec x, the x axis and the lines x=pi/3 and x=-pi/3 giving your answer to 2dp.

So, I had my ordinates for trapezium rule spaced at pi/6 and drew a table...

x -pi/3 -pi/6
sec x 2 2/rt.3

etc...

and then did...

pi/6 [2+2+2(1+2/rt.3+2/rt.3)]

So which bit am I doing wrong?
2. are you sure that you get the same results for the positive and negative values of x...

because you've only given the negative x values in the table

soz, i cant remeber if the sec x graph was symmetrical or not
3. Yeah, you do, that's why I haven't typed out the whole table... well the real reason was that I couldn't format it. Anyway, it's symmetrical, because my graph was symmetrical and according the answers, my graph is correct.
4. (Original post by Charlottie)
pi/6 [2+2+2(1+2/rt.3+2/rt.3)]

So which bit am I doing wrong?
trapezium rule: 0.5 * h * (a + b + 2(c + d +...)) right?
so you'd need to divide it by 2?

where a/b/c/d/etc are the y values

i'd imagine theres more to it than that and i've just missed something
5. ahhh, that must be it, forgotten to divide by two. I just had it as... (cheesy maths teacher's way of saying it)...

my first, plus my last, plus my everything twice, times by the height (must be times by the height divided by two)
6. ah thats alright then, the formula is given in the exam (i think) so you'd (in theory) notice things like that
7. *Checks formulae book*... I can't find it, which page? I'll remember it now anyway.

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