sinA / cos(A/2) = sinB / cos(B/2) = sinC / cos(C/2)为什么等于sinA/2=sinB/2=sinC/2

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sinA/cos(A/2)=sinB/cos(B/2)=sinC/cos(C/2)为什么等于sinA/2=sinB/2=sinC/2sinA/cos(A/2)=sinB/cos(B/2)=sinC/c

sinA / cos(A/2) = sinB / cos(B/2) = sinC / cos(C/2)为什么等于sinA/2=sinB/2=sinC/2
sinA / cos(A/2) = sinB / cos(B/2) = sinC / cos(C/2)为什么等于sinA/2=sinB/2=sinC/2

sinA / cos(A/2) = sinB / cos(B/2) = sinC / cos(C/2)为什么等于sinA/2=sinB/2=sinC/2
sin(x)=2sin(x/2)cos(x/2).代入即得.