tanB=0.5,求角B

tanA+tanB+根号3=根号3tanA*tanBtanA+tanB=根号3（tanA*tanB-1）（tanA+tanB）/（1-tanAtanB）=-根号3=tan(A+B)A+B∈（0,π）A

由tana=0.5得sin2a=2*0.5/(0.5^2+1)=4/5cos2a=(1-0.5^2)/(1+0.5^2)=3/5sin(2a+b)=sin2a*cosb+cos2a*sinb=4/5c

1.tanA-tanB/tanA+tanB=c-b/c是不是(tanA-tanB)/(tanA+tanB)=(c-b)/c?是的话,现在就解吧.假如是(tanA-tanB)/(tanA+tanB)=(

sin(a+b)=0.5,sin(a-b)=1/3,两式相加得sinacosb=5/12sinbcosa=1/12tana/tanb=(sinacosb)/(sinbcosa)=5

(tanA-tanB)/(tanA+tanB)=(sinAcosB-sinBcosA)/(sinAcosB+sinBcosA)=(sinAcosB-sinBcosA)/sin(A+B)=(sinAco

由正弦定理有a/c=sinA/sinC因为(2a-C)/C=tanB/tanC所以2a/c-1=tanB/tanC2sinA/sinC-1=sinBcosC/cosBsinC2sinAcosB-cos

LZ,∠A=60度.\x0d\x0d(tanA-tanB)/(tanA+tanB)=1-2tanB/(tanA+tanB)\x0d(c-b)/c=1-b/c\x0d由已知可得,\x0d2tanB/(t

∠A=60度.(tanA-tanB)/(tanA+tanB)=1-2tanB/(tanA+tanB)(c-b)/c=1-b/c由已知可得,2tanB/(tanA+tanB)=b/c=sinB/sinC

（1）由题设c²=a²+b²-ab及余弦定理cosC=(a²+b²-c²)/(2ab)可知,cosC=1/2.(0＜C＜180º)

已知Rt△ABC中,角C=90°则a^2+b^2=c^2(1)a,b,c成等差数列则a+c=2bc=2b-a代入(1)a^2+b^2=4b^2-4ab+a^2所以4a=3ba/b=3/4b/a=4/3

tanA/tanB=sinAcosB/(cosAsinB)=2sinC/sinB-1sinAcosB=2sinCcosA-cosAsinBsin（A+B）=2ssinCcosA=sinCcosA=1/

题目应该是在三角形ABC中若（a^2-b^2+c^2)tanB=根号3倍ac求角B2acCosB*tanB=2acsinB=根号3倍ac2sinB=根号3sinB=根号3/2是60或120度

a+b=a/tanA+b/tanBa（1-1/tanA）+b(1-1/tanB)=0a(1-cosA/sinA)+b(1-cosB/sinB)=0根据正弦定理a/sinA=b/sinB那么sinA(1

tanA/tanB=(2c-b)/bsinA*cosB/(cosA*sinB)=(2c-b)/b[a*(a^2+c^2-b^2)/2ac]/[b*(b^2+c^2-a^2)/2bc]=(2c-b)/b

sinA*cosB/(cosAsinB)=（√2c-b）/b,根据正弦定理,sinC/sinB=c/b,（√2c-b）/b=√2sinC/sinB-1,sinA*cosB/(cosAsinB)=√2s

tanA/tanB=sinAcosB/sinBcosAc=2RsinCb=2RsinB所以2x2RsinC-2RsinB/2RsinB=2sinC-sinB/sinB所以sinAcosB/sinBco

(tanA+tanB)/(1-tanA*tanB)=-1两边同乘以(1-tanA*tanB),等式两边就为(tanA+tanB)=-(1-tanA*tanB),“-“(1-tanA*tanB)注意这个

tan(A+B)=4=(tanA+tanB)/(1-tanAtanB)tanAtanB=1/2tanA

tanA=tan(180-B-C)=-tan(B+C)=-[(tanB+tanC)/(1-tanB*tanC)]=-31/(cosA)^2=(secA)^2=(tanA)^2+1=10所以(cosA)