solve the triangle using either the Law of Sines or the Law of Cosines.Round your answers to the nearest tenth. a = 12, b = 14, c = 21

Question

anonymous · Answer

solve for the largest angle first, which will be the angle opposite the longest side $c$

anonymous · Answer

$$\cos(C)=\frac{a^2+b^2-c^2}{2ab}$$ in your case 
$$\cos(C)=\frac{12^2+14^2-21^2}{2\times 12\times 14}=-\frac{101}{336}$$

anonymous · Answer

arccosine of $-\frac{101}{336}$ is $107.5^o$ and that is your largest angle
now go to the law of cosines

anonymous · Answer

thanks!

anonymous · Answer

yw

anonymous · Answer

I would use the sine law to solve the rest of the triangles. Far easier.

anonymous · Answer

ooops man i am screwing up all night
that is what i meant "then go to the law of sines" much easier

anonymous · Answer

@satellite73 : It's fine: I said the square root of 2 was 1 once.

anonymous · Answer

yeah an sometimes $(\frac{1}{2})^2=1$ as well

anonymous · Answer

Hehe...