三角形ABC中，a,b,c是A,B,C所对的边，S是该三角形的面积，且cosB/cosC=—（b/（2a+c）。(1)求角B

显示全部楼层 · 2011-6-30 00:58:57

在三角形ABC中角A,B,C所对的边分别为a,b,c，S，为该三角形的面积，且cosB/cosC=—（b/（2a+c）。(1)求角B.。（2）若a=4,S=3√5，求b

千问 · 2011-6-30 00:58:57

Riley went to the Miami Heat training camp guide Riley "Sun Sentinel" message, the NBA (microblogging) summer league this coming year, no arrangements, and so the Heat can only be organized their very own three-day "mini-training camp" to review the rookie who voted. Heat president Pat Riley - personally found the...

千问 · 2011-6-30 00:58:57

边化角或者角化边，再用正余弦定理，还有S=0。5*ab*sinC面积公式...

千问 · 2011-6-30 00:58:57

1a/sinA=b/sinB=c/sinC=kcosB/cosC=-b/(2a+c)cosB/cosC=-sinB/(2sinA+sinC)cosBsinC+2sinAcosB=-sinBcosCsinA=-2sinAcosBcosB=-1/2b=1202c=2S/asinB=6√5/(2√3)=√15b^2=a^...