a^2=b^2+c^2-2bccosA.

b^2=a^2+c^2-2accosB.

c^2=a^2+b^2-2abcosC.

Sinusoidal propaganda

a=2RsinA，

b=2RsinB，

c=2RsinC。

rare

-The radius of the circumscribed circle of the triangle.

a/sinA=b/sinB=c/sinC