Can you use the Law of Cosines in the triangle below? Why or why not?

http://www.aventalearning.com/courses/GEOMx-HS-A09/b/assessments/R-LawofCosinesShortAnswerQuiz/Geometry_8.4.14_Quiz_FINAL_4q.gif

Question

Can you use the Law of Cosines in the triangle below? Why or why not?


http://www.aventalearning.com/courses/GEOMx-HS-A09/b/assessments/R-LawofCosinesShortAnswerQuiz/Geometry_8.4.14_Quiz_FINAL_4q.gif

anonymous · Answer

you can use it for any triangle, there are no restrictions

vera_ewing · Answer

@mukushla

vera_ewing · Answer

@mukushla I know that I can use the Law of Cosines, but idk why?

amistre64 · Answer

the law of cosine requires 3 parts to solve a 4th unknown.

$$(leg_c)^2=(leg_a)^2+(leg_b)^2-2(leg_a)(leg_b)~cos(\angle ab)$$
got no good way to present the angle between a and b in latex

amistre64 · Answer

$$c^2=a^2+b^2-2ab\cos(C)$$
iff all we know are a,b,c  then yes, we can solve for angle C