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C2 Trignometry Watch

1 i) Express sin2x + cos(90-2x) in terms of a single trig function.

ii) Find all values of x in the interval 0<x<360 for which sin2x+cos(90-2x) = -1

2) Find the least positive value of angle A for which sin A = 0.2 and cos A is negative.

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The first one I'm not sure how to do it now that they're are both sin and cos involved

Second one, I'm not sure how to go about doing it.
2. For Q1 have you tried using the angle-addition formula for ? Then you use your answer to do part (ii).

For Q2, I assume you mean "least positive" rather than "least possible"? You'll find that there are infinitely many values of for which , but for some of these, will be positive, and for the others it will be negative. You need to find the first one such that .
3. RIP
4. 1)I dont think I've done that angle addition formula thing yet .

2) I'll try doing it soon.
5. (Original post by Rahul.S)
RIP
6. What exam board are you on WildBerry?

I'm on edexcel and haven't come across any questions like these.
7. (Original post by Thrug)
What exam board are you on WildBerry?

I'm on edexcel and haven't come across any questions like these.
I'm on OCR, they're from the Misc exercise of their textbook, the topics are usually harder than normal questions .
8. Wow.. My C2 wasn't as hard as this
9. (Original post by WildBerry)
1)I dont think I've done that angle addition formula thing yet .

2) I'll try doing it soon.
Thinking about it, angle-addition formulae don't come up until C3. In that case, draw a graph of and on the same axes, and work out what graph transformations are necessary to turn the sine graph into the cosine graph. Then using your C1 knowledge of graph transformations, you'll be able to write in terms of .
10. (Original post by xPixie)
Wow.. My C2 wasn't as hard as this
I've been told to do around 15 questions like these

I've done 10, but there are around 5 more really hard ones that I just dont know how to start. I'll probably just do what I can after doing these, and get the usual C grade written on for not attempting the rest, even though the crap teacher hasn't taught any of this yet.
11. (Original post by WildBerry)
I've been told to do around 15 questions like these

I've done 10, but there are around 5 more really hard ones that I just dont know how to start. I'll probably just do what I can after doing these, and get the usual C grade written on for not attempting the rest, even though the crap teacher hasn't taught any of this yet.
Q1i sounds like a C4 question & I've just started that now
What board are you? Because I'm on OCR MEI, and their papers aren't as hard as this. If you want to revise, just do past papers, that's the best way to revise maths
12. (Original post by xPixie)
Q1i sounds like a C4 question & I've just started that now
What board are you? Because I'm on OCR MEI, and their papers aren't as hard as this. If you want to revise, just do past papers, that's the best way to revise maths

Normal OCR .

I looked at a couple of past papers for these questions, and they're so confusing Eg the interval is in terms of Pie . Eg 9 : http://www.ocr.org.uk/download/pp_08...l_gce_4722.pdf
13. (Original post by WildBerry)
Normal OCR .

I looked at a couple of past papers for these questions, and they're so confusing Eg the interval is in terms of Pie . Eg 9 : http://www.ocr.org.uk/download/pp_08...l_gce_4722.pdf
I have the same questions :P
14. Ah well I can do intervals in terms of pi, but not what you have mentioned above.
15. (Original post by WildBerry)
use sin and cos to derive to tan. 4rm there its easy!

RIP WildBerry

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Updated: December 13, 2010
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