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C3 Trig Question, Help? (attached) watch

1. I know how to do every part, apart from part C) where it asks to find t
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2. (Original post by chrlhyms)
I know how to do every part, apart from part C) where it asks to find t
Ah the ferris wheel question - a very common question in the maths forum

You say you can't find t but does that mean you've already found the maximum value of H? Please post all your working / thoughts.
3. Try rewriting the H equastion in th Rcos ("") form and then think about ways you can maximise your H value
4. (Original post by chrlhyms)
I know how to do every part, apart from part C) where it asks to find t
what a classic, i remember i struggled on this , now if i remember.

The max value of H means to make H as big as possible.

So what can you do to the cos thing you now got from part a to make H as big as possible?
Set it equal to 0? -1? or 1? what gives you the biggest value of H
5. (Original post by Notnek)
Ah the ferris wheel question - a very common question in the maths forum

You say you can't find t but does that mean you've already found the maximum value of H? Please post all your working / thoughts.
So i've found H as 10 + root(85)
and the equation of H as

H=10-root85 cos(pit/5 +0.2187)
but cant think how I would find the maximum value of t as surely this would be 1 but the MS says -1?
6. (Original post by chrlhyms)
So i've found H as 10 + root(85)
and the equation of H as

H=10-root85 cos(pit/5 +0.2187)
but cant think how I would find the maximum value of t as surely this would be 1 but the MS says -1?
If cos(pit/5 +0.2187) = 1 then

10-root85 cos(pit/5 +0.2187) = 10 - root85

But you said the maximum was 10 + root85 so cos(pit/5 +0.2187) must be -1.
7. (Original post by Notnek)
If cos(pit/5 +0.2187) = 1 then

10-root85 cos(pit/5 +0.2187) = 10 - root85

But you said the maximum was 10 + root85 so cos(pit/5 +0.2187) must be -1.
Sorry, I still dont understand!
8. (Original post by chrlhyms)
Sorry, I still dont understand!
How did you find that the maximum value of H is 10 + root(85)? Please explain fully.
9. (Original post by Notnek)
How did you find that the maximum value of H is 10 + root(85)? Please explain fully.
well since the original equation was stretched by a factor of root 85, the new equation was +10 onto that, therefore the new maximum was 10 + root85 and minimum 10-root85
10. (Original post by Notnek)
If cos(pit/5 +0.2187) = 1 then

10-root85 cos(pit/5 +0.2187) = 10 - root85

But you said the maximum was 10 + root85 so cos(pit/5 +0.2187) must be -1.
if cos(pit/5) +0.2187)=-1
then surely 10-root85 cos(pit/5) +0.2187)= -10+root85
which isnt the max?
11. (Original post by chrlhyms)
if cos(pit/5) +0.2187)=-1
then surely 10-root85 cos(pit/5) +0.2187)= -10+root85
which isnt the max?
I'll write it using brackets to make it clearer:

So when

you get

12. (Original post by Notnek)
I'll write it using brackets to make it clearer:

So when

you get

perfect! I understand now thank you! that question was horrible
13. (Original post by chrlhyms)
perfect! I understand now thank you! that question was horrible
Yes it was a bit nasty. They've asked a ferris wheel type question a few times in C3 exams so it's worth practicing them
14. (Original post by Notnek)
Yes it was a bit nasty. They've asked a ferris wheel type question a few times in C3 exams so it's worth practicing them
at least now i will know how to solve it! thank you!

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