cosC=1/2=(a^2+b^2-c^2)/2ab
所以a^2+b^2-c^2=ab
a^2+b^2=ab+c^2
a/(b+c)+b/(a+c)
通分=(a^2+ac+b^2+bc)/(ac+bc+ac+c^2)
=(ab+c^2+ac+bc)/(ac+bc+ac+c^2)
=1
cosC=1/2=(a^2+b^2-c^2)/2ab
所以a^2+b^2-c^2=ab
a^2+b^2=ab+c^2
a/(b+c)+b/(a+c)
通分=(a^2+ac+b^2+bc)/(ac+bc+ac+c^2)
=(ab+c^2+ac+bc)/(ac+bc+ac+c^2)
=1