hey, I was just wondering when i would use sine law, opposed to cosine law and vice-versa.
Thanks!
You don't mean Law of Sines and Law of Cosines, right?
If you mean the law of sine, that is: $\displaystyle Sin\,\theta = \frac{opp}{hyp}$
And the law of cosine: $\displaystyle Cos\,\theta = \frac{adj}{hyp}$
Then you can use use either of them when you have a right triangle.
Which one depends on what you know, be it the opposite side, adjacent side, or the hypotenuse.
You use the law of sines when you have two known angles and one known side in a triangle (AAS, ASA).
Law of Sines: $\displaystyle \frac{\sin(\alpha)}{A}=\frac{\sin(\beta)}{B}=\frac {\sin(\gamma)}{C}$
You use the law of cosines when you have two known sides and one known angle (triangle is SAS).
$\displaystyle \begin{aligned}
\text{Law of Cosines: }&A^2=B^2+C^2-2BC\cos(\alpha) \\
&B^2=A^2+C^2-2AC\cos(\beta) \\
&C^2=A^2+B^2-2AB\cos(\gamma)
\end{aligned}$