C2 quick question- can anyone help me ^>^

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FloralEssence
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Okay, so, I am doing this maths question and I have a question- I understand everything except from this part which is bothering me quite a little bit.

I have print screened it, as there are diagrams to work from:


Image

I amcurrently on part iii:

and this is what the guy from exam solutions did:

Image

but I don't understand something: Why did he use the formula 1/2 absinC (2nd step) I thought- couldn't you have just divided the triangle in half and worked out the area of the triangle using b*h/2 and then proceed to the other steps?

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It is just a small thing but I need to understand why, plus that way I don't want to have to wait until Monday to ask my maths teacher.
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Muttley79
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Isn't it because we don't know CD without calculating it and that is another step?
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Kevin De Bruyne
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(Original post by FloralEssence)
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If you wanted to, you could use pythagoras to find h and it will give you the same answer. I suppose the formula is more direct.
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LibertyMan
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Yes... you could do that. It is an equally valid approach. (But remember you would have to time it by 2 afterwards to make it ACD).
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High Stakes
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I did it like this? Doesn't this work too?


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High Stakes
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Because we don't know what CD is. If you did split the triangle you could work out half of CD through Pythagoras.
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FloralEssence
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Thanks for all the responses ^>^, but isn't CD just equal to 12 as is AB=12 making the height or 1/2 of CD 6?
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FloralEssence
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(Original post by High Stakes)
I did it like this? Doesn't this work too?


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Oh, I hadn't thought of it that way:eek::eek: Thanks!
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High Stakes
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(Original post by FloralEssence)
Oh, I hadn't thought of it that way:eek::eek: Thanks!
No worries!
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JaseyRae
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(Original post by FloralEssence)
Okay, so, I am doing this maths question and I have a question- I understand everything except from this part which is bothering me quite a little bit.

I have print screened it, as there are diagrams to work from:


Image

I amcurrently on part iii:

and this is what the guy from exam solutions did:

Image

but I don't understand something: Why did he use the formula 1/2 absinC (2nd step) I thought- couldn't you have just divided the triangle in half and worked out the area of the triangle using b*h/2 and then proceed to the other steps?

________________________________ ______________

It is just a small thing but I need to understand why, plus that way I don't want to have to wait until Monday to ask my maths teacher.
It's easier to work out the area of the whole triangle using that equation. To use 1/2bh you'd have to split the triangle into two right angled triangles and then times the answer by two to get the whole triangle
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Chittesh14
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(Original post by FloralEssence)
Thanks for all the responses ^>^, but isn't CD just equal to 12 as is AB=12 making the height or 1/2 of CD 6?
CD is equal to 2 (root(7^2 - 6^2)) = 7.21 cm (2 d.p.)



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High Stakes
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(Original post by Chittesh14)
CD is equal to 2 (root(7^2 - 6^2)) = 7.21 cm (2 d.p.)



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Good old Pythagoras.
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Chittesh14
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(Original post by High Stakes)
Good old Pythagoras.
Yeh lol, I don't know how to answer the question haha, I'm only in year 10. But I knew Pythagoras, so I had a bit of an idea haha.


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High Stakes
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(Original post by Chittesh14)
Yeh lol, I don't know how to answer the question haha, I'm only in year 10. But I knew Pythagoras, so I had a bit of an idea haha.


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Lmao, that's good. If you can take what you learn from the early stages and apply it to more complicated questions you will arrive at an answer much faster. Being proficient at spotting out where you can apply what you've learned is also important.
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FloralEssence
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(Original post by Chittesh14)
Yeh lol, I don't know how to answer the question haha, I'm only in year 10. But I knew Pythagoras, so I had a bit of an idea haha.
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Lol, and thanks for the reply, I appreciate it. ^>^
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Chittesh14
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(Original post by FloralEssence)
Lol, and thanks for the reply, I appreciate it. ^>^
No problem :P, sometimes it is hard to understand questions. Like, I get stuck sometimes and end up understanding the question only after looking at the mark scheme, my mind just go blanks and then I'm usually like - omg, I'm so stupid lol.

(Original post by High Stakes)
Lmao, that's good. If you can take what you learn from the early stages and apply it to more complicated questions you will arrive at an answer much faster. Being proficient at spotting out where you can apply what you've learned is also important.
Haha, thanks man! It's not easy to understand, but sometimes your mind just becomes mathematical and you remember all these formulaes that you can apply to this certain question to work it out. Like, I would understand to use Pythagoras and have no idea what to do next, it'd take like like 2 minutes to explore the question and realise I could use Pythagoras here :P. I'm taking GcSE maths this year anyway so it'd be great to get A* haha and possibly to Additional Maths in year 11 lol not gonna do AS level maths hehe.
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FloralEssence
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(Original post by Chittesh14)
No problem :P, sometimes it is hard to understand questions. Like, I get stuck sometimes and end up understanding the question only after looking at the mark scheme, my mind just go blanks and then I'm usually like - omg, I'm so stupid lol.
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Samee! I feel so stupid when that happens because, it's not a matter of not knowing, it is just that sometimes the way the questions are worded or an extra symbol added can f* up your whole mind. :eek:
That is why I aim to use different sources/ exam board questions to broaden my understanding. For instance, that question up there is not from my original exam board (Edexcel) it's OCR and from looking at other OCR papers, I have noticed that the language used is not so similar to Edexcel's. :banana2::banana:
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Chittesh14
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(Original post by FloralEssence)
Samee! I feel so stupid when that happens because, it's not a matter of not knowing, it is just that sometimes the way the questions are worded or an extra symbol added can f* up your whole mind. :eek:
That is why I aim to use different sources/ exam board questions to broaden my understanding. For instance, that question up there is not from my original exam board (Edexcel) it's OCR and from looking at other OCR papers, I have noticed that the language used is not so similar to Edexcel's. :banana2::banana:
Haha, true. I don't do other exam boards paper, I don't know why. I've got every exam paper from edexcel printed out from like 2010 and done lol at least 2 times each . Going to make it a 3 by this summer lol.


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High Stakes
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(Original post by FloralEssence)
Samee! I feel so stupid when that happens because, it's not a matter of not knowing, it is just that sometimes the way the questions are worded or an extra symbol added can f* up your whole mind. :eek:
That is why I aim to use different sources/ exam board questions to broaden my understanding. For instance, that question up there is not from my original exam board (Edexcel) it's OCR and from looking at other OCR papers, I have noticed that the language used is not so similar to Edexcel's. :banana2::banana:

Yeah I do Edexcel too so I was a bit stumped when this OCR question popped up. But, that's what we want to avoid. We need to be able to apply our knowledge to a variety of different situations.
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