∵a/cosA/2=b/cosB/2
又∵a/sinA=b/sinB
∴sinA/sinB=(cosA/2) /(cosB/2)
=>sinAcosB/2=sinBcosA/2
=>2sinA/2cosA/2cosB/2=2sinB/2cosB/2cosA/2
=>sinA/2=sinB/2
∵A、B∈(0°,180°)
∴A/2=B/2
A=B
同理,B=C
所以三角形为等边三角形
∵a/cosA/2=b/cosB/2
又∵a/sinA=b/sinB
∴sinA/sinB=(cosA/2) /(cosB/2)
=>sinAcosB/2=sinBcosA/2
=>2sinA/2cosA/2cosB/2=2sinB/2cosB/2cosA/2
=>sinA/2=sinB/2
∵A、B∈(0°,180°)
∴A/2=B/2
A=B
同理,B=C
所以三角形为等边三角形