Question

The Cosine theorem: c^2=a^2-2*a*b*cos(C).

How to find the angles if you know all sides?

Answer 1

unless it's a specific type of triangle, you can't...i think...

Answer 2

i stand corrected...it seems you can...

Answer 3

I found the angle C but i can't find the others:

C=acos((c^2-a^2-b^2)/-2*a*b)

Answer 4

from that you can use sine law \[\sin A = \frac{a\sin C}{c}\]

Answer 5

since sine law states \[\frac{\sin A}a = \frac{\sin C}c\]
or are you not allowed to use that?

Answer 6

Yhea, Sin law is good. But does it work with the Cosine theorem?

Answer 7

if memory serves right... the three equations of cosine law constains 2 sides and 1 angle...so i think it's possible

Answer 8

C=acos((c^2-a^2-b^2)/(-2*a*b)
B=acos((b^2-a^2-c^2)/(-2*a*c)
A=acos((a^2-b^2-c^2)/(-2*b*c)

Ok, i found the solution.

Answer 9

congratulations

Answer 10

oh, i got 2 medals! thanks.

Answer 11

users who solve their own questions tend to get medals