a,b,c成等差数列:
2b=a+c
b/sinB=a/sinA=c/sinC=2R
2sinB=sinA+sinC
sinB=(sinA+sinC)/2
sinA,sinB,sinC成等比数列:
sin^2B=sinA*sinC
[(sinA+sinC)/2]^2=sinA*sinC
(sinA-sinC)^2=0
sinA=sinC
A=B=C=60°
等边三角形
a,b,c成等差数列:
2b=a+c
b/sinB=a/sinA=c/sinC=2R
2sinB=sinA+sinC
sinB=(sinA+sinC)/2
sinA,sinB,sinC成等比数列:
sin^2B=sinA*sinC
[(sinA+sinC)/2]^2=sinA*sinC
(sinA-sinC)^2=0
sinA=sinC
A=B=C=60°
等边三角形