# The damned triangle formulae

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#1
I've got a maths, sorry, mathEMATICs exam real soon and i don't know when or where or how to use the Sine and Cosine rule...someone help me and i'll bring your rep uuuup!
0
6 years ago
#2
(Original post by Nutella_Balls)
I've got a maths, sorry, mathEMATICs exam real soon and i don't know when or where or how to use the Sine and Cosine rule...someone help me and i'll bring your rep uuuup!

So if we look at the labelled triangle.

Use the sine rule if you have two sides and their corresponding angles. For example A and a, with B and a. Your missing angle/side will be part of these pairs.

You can use the sine rule to find an angle or a side. Whatever you're finding will be the numerator. So if you're finding a side, both numerators are your side lengths (one which is unknown and one which is known) and the denominators will be your angles - remember to do sin(90) if the angle is 90 not just 90.

If you're finding an angle, you do the opposite, so the two numerators will be the sine angle things. When calculating an angle, ensure than you do the inverse sign of it - i.e. sin^-1(your rearranged formula).

Use the cosine rule if you have two sides and an angle between those two sides. You can then rearrange it for different lengths and angles.

Watch a video on youtube if it doesn't make sense. Also make sure you're confident in rearranging the sine rule!
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#3
(Original post by jamestg)

So if we look at the labelled triangle.

Use the sine rule if you have two sides and their corresponding angles. For example A and a, with B and a. Your missing angle/side will be part of these pairs.

You can use the sine rule to find an angle or a side. Whatever you're finding will be the numerator. So if you're finding a side, both numerators are your side lengths (one which is unknown and one which is known) and the denominators will be your angles - remember to do sin(90) if the angle is 90 not just 90.

If you're finding an angle, you do the opposite, so the two numerators will be the sine angle things. When calculating an angle, ensure than you do the inverse sign of it - i.e. sin^-1(your rearranged formula).

Use the cosine rule if you have two sides and an angle between those two sides. You can then rearrange it for different lengths and angles.

Watch a video on youtube if it doesn't make sense. Also make sure you're confident in rearranging the sine rule!
Whatchu talkin' bout...REARRANGING the sine rule?? Surely they won't ask me that....will they?
0
6 years ago
#4
(Original post by Nutella_Balls)
Whatchu talkin' bout...REARRANGING the sine rule?? Surely they won't ask me that....will they?
Yeppers - it's easy to rearrange you just flip everything upside down. (Not sure how to post formulas on TSR, but Google it you'll see the rearranged version)

On an unrelated note, you also need to be able to rearrange the cosine rule, which I find awful to rearrange - best idea is to learn the rearranged version (as they give you the normal one), unless you are confident in rearranging.
0
6 years ago
#5
(Original post by Nutella_Balls)
Whatchu talkin' bout...REARRANGING the sine rule?? Surely they won't ask me that....will they?
They will and it's super duper easy!
0
6 years ago
#6
- sine rule, normal and rearranged. Very simple to do
0
6 years ago
#7
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#8
(Original post by jamestg)
I took that trip two weeks ago. Not useful. Any channels in particular?
Oh but thats for that pic, I'll be sure to make it my screensaver
0
6 years ago
#9
(Original post by Nutella_Balls)
I took that trip two weeks ago. Not useful. Any channels in particular?
Oh but thats for that pic, I'll be sure to make it my screensaver
0
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