lailiww
幼苗
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根据正弦定理:
AB/SINC=AC/SINB=BC/SINA
4/sin^2 C=(m^2+2m+4)/sin^2 B=(m+2-2m+4)/sin^2 A
4=(m^2+2m+4)*sin^2 C/sin^2 B=(m+2-2m+4)*sin^2 C/sin^2 A
sin^2 A=(m^2+2m+4)*sin^2 C/4
sin^2 B==(m^2-2m+4)*sin^2 C/4
代入sin^2 A + sin^2 B = 2sin^2 C
(m^2+2m+4)/4+(m^2-2m+4)/4=2
m^2+4=4
m=0
1年前
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