cosine rules

Discussion in 'Math' started by amilton542, Jan 30, 2011.

1. amilton542 Thread Starter Active Member

Nov 13, 2010
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ive been working on sine and cosine rules out this book, but they only do one example of each so ive had to rearrange them for the complete set but i still end up with the same angle using either, just need some clarification wether there right:

for e.g a/SIN A = b/SIN B = c/SIN C ,

a = c x SIN A/SIN C. SIN A = a x SIN B/B

b = a x SIN B/SIN A. SIN B = b x SIN C/C

c = b x SIN C/SIN B. SIN C = c x SIN A/A

Last edited: Jan 30, 2011
2. Georacer Moderator

Nov 25, 2009
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Can you include parenthesis and keep the notation constant to be more specific?
They seem right but I can't be sure if you alternate the letter for the sides from small to capital.

3. amilton542 Thread Starter Active Member

Nov 13, 2010
496
64
TWO ANGLES given plus ANY SIDE
a = b x SIN A / SIN B
b = c x SIN B / SIN C
c = b x SIN C / SIN B

TWO SIDES given plus an ANGLE NOT ENCLOSED by them
SIN A = a x SIN B / b
SIN B = b x SIN C / c

ive created numerous triangles and i think this is write so far but for SIN C theres two where the answer is very close for each and i dont no what ones write:
SIN C = c x SIN B / b (i believe this may be the correct one)
SIN C = c x SIN A / a

Nov 9, 2007
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5. Georacer Moderator

Nov 25, 2009
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All of your formulas are correct, but be careful when trying to find an angle, as Papabravo stated. You will get 2 answers and you must use your intuition and problem data to filter the wrong one.

The video linked is very informative.

6. studiot AAC Fanatic!

Nov 9, 2007
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Have I been promoted?

7. Georacer Moderator

Nov 25, 2009
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I don't know about you, but E-book Developer is the highest rank I 'd like to have. Any higher and it would be too much work on the site to keep me interested in.

8. studiot AAC Fanatic!

Nov 9, 2007
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It's not all milk and honey you know.
Especially since they won't adopt my suggestion of free beer for this rank.

No, by promotion I was thinking of being compared to papabravo and his ghost presence in this thread.

9. Georacer Moderator

Nov 25, 2009
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Free beer, eh? I 'm not in heaven yet, so I guess I can't have any.

As for your rep, I can't verify it personally, only time can.
Especially if you consider the phrase that says "Only after someone's death you can judge him properly", or something like that.

I for once, don't want to compete for the position of the "Math guru". What I would like however is the visitor of the site to acknowledge the time I spend here and that I generally provide correct answers.