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1. Core 2 simple question

For part b I used the formula COSA = b^2 + c^2 - a^2 / 2bc

I got the answer 66.2 to 3.sf, but the answer in the mark scheme is 66.4 but they used a different formula, does any one know why I didn't get what they got, they used the cosine formula re-arranged to find an angle.

Thanks
2. Re: Core 2 simple question
Sorry, I would help, but can't see the picture, any chance you can link the question or type it?
3. Re: Core 2 simple question
(Original post by IShouldBeRevising_)

For part b I used the formula COSA = b^2 + c^2 - a^2 / 2bc

I got the answer 66.2 to 3.sf, but the answer in the mark scheme is 66.4 but they used a different formula, does any one know why I didn't get what they got, they used the cosine formula re-arranged to find an angle.

Thanks
This is the formula COSA = (b^2 + c^2 - a^2) / 2bc but I expect you rounded too soon. Use exact values and ONLY round when giving the FINAL answer.

I think one measurement was rounded to 18.4 BUT the value you should use is either the exact value (from calculator memory) or 18.441
4. Re: Core 2 simple question
Yeah, make sure you have rearranged properly

remember to always use brackets on a calculator.
5. Re: Core 2 simple question
(Original post by steve2005)
This is the formula COSA = (b^2 + c^2 - a^2) / 2bc but I expect you rounded too soon. Use exact values and ONLY round when giving the FINAL answer.

I think one measurement was rounded to 18.4 BUT the value you should use is either the exact value (from calculator memory) or 18.441
Oh yeah true I did use the rounded answer, maybe that is why, but I used a different formula from the mark scheme would I still get the full marks?
6. Re: Core 2 simple question
If you got the same kind of answer I can see you losing 1 mark for using a rounded answer. If you are using any good calculator that wasn't bought from a hobo in the street, such as the Casio scientific ones use STO--> and pick a letter stores the whole answer it is awesome for trig questions and S1 regression lines.
7. Re: Core 2 simple question
(Original post by Booyah)
If you got the same kind of answer I can see you losing 1 mark for using a rounded answer. If you are using any good calculator that wasn't bought from a hobo in the street, such as the Casio scientific ones use STO--> and pick a letter stores the whole answer it is awesome for trig questions and S1 regression lines.
Unfortunately I use a potato to do my calculations bought from a hobo on the street #firstworldpains

Just messing with you thanks for the STO thing didn't know that before
Last edited by IShouldBeRevising_; 17-05-2012 at 09:54.
8. Re: Core 2 simple question
(Original post by IShouldBeRevising_)
Unfortunately I use a potato to do my calculations bought from a hobo on the street #firstworldpains

Just messing with you thanks for the STO thing didn't know that before
lol @potato

What is STO?
9. Re: Core 2 simple question
(Original post by 007Shella)
lol @potato

What is STO?
A button on your calculator. If you have a number like 5.34786435 come up click STO and then click one of the letters on your calculator (should at least have A, B, C, D, E) and then that number will be stored in that letter.

So later you can type A/5 + 7 and get an answer with no rounding.
10. Re: Core 2 simple question
(Original post by hassi94)
A button on your calculator. If you have a number like 5.34786435 come up click STO and then click one of the letters on your calculator (should at least have A, B, C, D, E) and then that number will be stored in that letter.

So later you can type A/5 + 7 and get an answer with no rounding.
Oh I see.... Thank you!
11. Re: Core 2 simple question
(Original post by hassi94)
A button on your calculator. If you have a number like 5.34786435 come up click STO and then click one of the letters on your calculator (should at least have A, B, C, D, E) and then that number will be stored in that letter.

So later you can type A/5 + 7 and get an answer with no rounding.
Well it will be to 12 sig figs.
12. Re: Core 2 simple question
(Original post by FranticMind)
Well it will be to 12 sig figs.
Of course, I meant no rounding from a human (and the best the exam board can expect ).