| Forum Home | ||||
| Press F1 | ||||
| Thread ID: 50227 | 2004-10-14 08:57:00 | [ OT ] Cosine Rule | ApeNz (4220) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 281086 | 2004-10-14 08:57:00 | HI , I was wondering if anyone knew how the cosine rule is Derived , the rule is a2 = b2 + c2 - 2 xbc * cos (angle) - the twos at the front are meant to be to the power of twos. Thanks Ape |
ApeNz (4220) | ||
| 281087 | 2004-10-14 08:59:00 | rule is a2 ( power of two ) = b2 ( power of two ) + c2 ( power of two ) - 2 * bc cos ( angle ) | ApeNz (4220) | ||
| 281088 | 2004-10-14 09:12:00 | Do you REALLY have to get my brain going? :( c2 = a2 + b2 - a·sin(B)·b·sin(A) - a·sin(B)·b·sin(A) + 2ab·cos(A)·cos(B) = a2 + b2 + 2ab(cos(A)cos(B) - sin(A)sin(B)) = a2 + b2 + 2ab(cos(A + B)) = a2 + b2 + 2ab(cos(180o - C)) = a2 + b2 - 2ab(cos(C)) As you would know, they 2's after the a and b's are squares, while the other ones are multiples. If you get stuck, get back and ask. Google does produce much decent answers for this though. Hope you haven't forgotten it :D |
~~~~~ s y ~~~~~ (2054) | ||
| 281089 | 2004-10-14 09:14:00 | Written as a^2 = b^2 + etc. It's derived from page 73 in my old book ;) |
R2x1 (4628) | ||
| 281090 | 2004-10-14 11:44:00 | I think they give you one equation in the exam (is that right?) and then you can easily re-arrange them to suit yourself for working out the question. | alphazulusixeightniner (185) | ||
| 281091 | 2004-10-14 19:25:00 | Thanks , yeah they do give it in the exam , i just wanted to know how they got it - helps me understand things more | ApeNz (4220) | ||
| 281092 | 2004-10-15 03:44:00 | what maths are you doing? year 11 or year 12?? last year in maths (year 11) there was a trig paper but it never had the cosine rule. actually we did the cosine this year in maths but it was a internal. im 99.9999999% sure that this isnt in the exams |
Prescott (11) | ||
| 281093 | 2004-10-15 04:28:00 | hehehe, Soh Cah Toa. | Jams (1051) | ||
| 281094 | 2004-10-15 05:55:00 | I hate trig, wait a second, i hate maths slash school altogether! - David |
DangerousDave (697) | ||
| 281095 | 2004-10-15 06:17:00 | trig isnt that bad, its not that hard either | Prescott (11) | ||
| 1 2 3 4 5 6 | |||||