Matric Relations On A Triangle

[Aladdin]

Questions : 1* By using the the Law of Sines find the relation that give the radius of the circumscribed circle and the are of the triangle ?

Law of sines : a/sin(A) = b/sin(B) = c/sin(C)

I searched on several websites is says that it also equals to 2R , R the raduis of the circumscribed circle .

2* Prove that a^2 = b^2 + c^2 -2bc cos(A) .

Thanks in advance ,
Aladdin

 

[mmm4444bot]

Here's some information that should help.

Proofs - Law of Cosines

Law of Sines - Triangle Area

(Can't say more, now; I don't feel good at all. )