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# C2 Trig Question: watch

1. I don't really know where to start..

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2. Have you drawn a diagram yet?

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3. (Original post by danconway)
Have you drawn a diagram yet?

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That's where I got stuck. I didn't really know how to visualise it in this case :/
4. (Original post by creativebuzz)
That's where I got stuck. I didn't really know how to visualise it in this case :/

Would you agree?

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5. (Original post by danconway)

Would you agree?

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Yup, I would agree! And we want to find the remaining side, however we don't know any of the interior angles so we can't perform trigonometry :/
6. (Original post by creativebuzz)
Yup, I would agree! And we want to find the remaining side, however we don't know any of the interior angles so we can't perform trigonometry :/
Cosine rule
7. Do some angle chasing first, and you'll see why it works (obviously you'll need the angle before you can use the cosine rule ). Think 'F-angles'.
8. (Original post by danconway)
Do some angle chasing first, and you'll see why it works (obviously you'll need the angle before you can use the cosine rule ). Think 'F-angles'.
I can't seem to find the angle :/
9. (Original post by creativebuzz)
I can't seem to find the angle :/
It's well hidden! Look around the point with the 138º angle on it. Work out anything you can find (even if it might seem insignificant!).
10. (Original post by danconway)
It's well hidden! Look around the point with the 138º angle on it. Work out anything you can find (even if it might seem insignificant!).
Well I guess I could do 180-138 = 42 and that will give me that tiny angle but I don't know..
11. (Original post by creativebuzz)
Well I guess I could do 180-138 = 42 and that will give me that tiny angle but I don't know..
If I told you that that 42º pops up somewhere else and is VERY handy, what would you say?
12. (Original post by danconway)
If I told you that that 42º pops up somewhere else and is VERY handy, what would you say?
I would say that 42 also an interior angle because of the alternate segment theorem or..?
13. (Original post by creativebuzz)
I would say that 42 also an interior angle because of the alternate segment theorem or..?
Probably doesn't work... 42 is just anti-clockwise of the 251, going from North on that point anticlockwise to the line joining the first point and that point.... Because corresponding angles.
14. That kinda idea.

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15. (Original post by danconway)
Probably doesn't work... 42 is just anti-clockwise of the 251, going from North on that point anticlockwise to the line joining the first point and that point.... Because corresponding angles.
I don't see it :/
16. (Original post by creativebuzz)
I don't see it :/

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17. Ohh I see now! Thank you! Damn, I really need to scratch up on my basic angle facts, would you advice just doing a couple of questions on basic angles?
18. (Original post by creativebuzz)
Ohh I see now! Thank you! Damn, I really need to scratch up on my basic angle facts, would you advice just doing a couple of questions on basic angles?
Well it seems that they'd definitely help! You can always have a quick check on here to revise them
19. (Original post by danconway)
Well it seems that they'd definitely help! You can always have a quick check on here to revise them
Yeah, I feel like I need to brush up on my basics, because they always come back to haunt me! :P But thank you for being so patient with me (positive rating given to show appreciation)!
20. (Original post by creativebuzz)
Yeah, I feel like I need to brush up on my basics, because they always come back to haunt me! :P But thank you for being so patient with me (positive rating given to show appreciation)!
Aha aw, well anything to help, and thanks for the rep!

I'll be off to bed – have fun with the rest of the problem (although going to bed is a great idea for everyone!); I can always help more tomorrow if you need it, but hopefully you can work it out from here!

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Updated: January 4, 2015
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