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# C3 trig Question Watch

1. Hi, i have another C3 question. Its on another topic so i started another thread (If that is that ok?)
https://7c95ed1f832973eac0c6e1a52b08...20C3%20OCR.pdf
Im an extremely lost on question 9(iii).
I looked at the market scheme and it said to "Attempt to relate k to at least 2 6sin 30".
I Cant see how this would help?

2. (Original post by SamuelN98)
Hi, i got another C3 question. Its on another topic so i started another thread (Is that ok?)

https://7c95ed1f832973eac0c6e1a52b08...20C3%20OCR.pdf
Im an extremely lost on question 9(iii).
I looked at the market scheme and it said to "Attempt to relate k to at least 2 6sin 30".
Cant see how this would help?
Can you see (i) of the question? Multiply through by 6 and compare the RHS. (the angles have to be divided by 1/3 as well)

We get .

You know that since is bounded between -90 and +90 then we have being bounded by -30 and +30.

So is bounded between -1/2 and +1/2.

So is bounded between 0 and 1/4.

So is bounded between...?
3. (Original post by Zacken)

Can you see (i) of the question? Multiply through by 6 and compare the RHS. (the angles have to be divided by 1/3 as well)

We get .

You know that since is bounded between -90 and +90 then we have being bounded by -30 and +30.

So is bounded between -1/2 and +1/2.

So is bounded between 0 and 1/4.

So is bounded between...?
So, that gives the upper bound of 3/2 , how do you get the lower bound?
4. (Original post by SamuelN98)
So, that gives the upper bound of 3/2 , how do you get the lower bound?
0.

0 * 6 is still 0.

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