Ambiguous Case of the Sine Rule

[kenhung123]

I am very worried about this concept because I have encountered a few problems that seemed to have a better answer when taking the bigger angle (180-a). However, it is very apparent, like the other answer was still possible. E.g. The angle must be >90 and <180. Answers can be 91 or 169 due to properties of sine ratios. So in the exam, is there anytime where only 1 answer is possible/accepted? (Will they give some type of warning at least)

[Albeno69]

yea i was confused bout this before my sac and teacher said it wont be on it so we bacially skipped it. but i think its a possibility for exams. especially that i would believe that alot of ppl would give 1 answer that would mean they would be wrong or get half marks.

[TrueTears]

sometimes you have to check if one of the 2 answers is plausible, because it might cause the total angle of the triangle to exceed 180.

[kenhung123]

Yea, the problem was in 1 question I encountered was that they both were suitable however, the other was like best fit since it just looked more appropriate to the size of angle presented.

[kenhung123]

yea i was confused bout this before my sac and teacher said it wont be on it so we bacially skipped it. but i think its a possibility for exams. especially that i would believe that alot of ppl would give 1 answer that would mean they would be wrong or get half marks.

I think you are meant to give 1 answer? But the problem is picking which answer I think?

[TrueTears]

they should give an initial condition, maybe say the angle has to be acute/obtuse etc?

[kenhung123]

Hopefully..

[kenhung123]

Nah, because in the case of the sine rule, you would only know 1 angle sometimes and 2 sides. So both angles can be a or 180-a to all add up to 180

[vexx]

Fair enough. Is the sine rule and cosine rule in methods?

no it's not.
further is silly.

[vexx]

LOL ^ so much for learning it
But it should be useful yeah? Say, we need it to solve a question or something...? Do we still get marks for using those formulae?

nahh it's not useful in what we do in methods, it's pretty much used (both sine rule and cos rule) for finding the side or angle of a triangle.. and we don't need to know that in methods, it's very very basic stuff; i wonder why i even come to class to learn it.
methods is far more interesting^^;
(im starting to like methods because of my hatred for further lol..)

[vexx]

it's pretty much used (both sine rule and cos rule) for finding the side or angle of a triangle

LOL yeah proving it is more fun!
Maybe you should have tried spesh Might suit you more.

haha i'm quite lazy, and not really into maths.. but i'm doing quite well at methods anyway, so i don't know.. probably wouldn't have done well since the amount of work i would have done would be too minimal haha.
goodluck for spesh though^^