若角a为锐角,且tana=3分之根号3

√3tan²α-4tanα+√3=0(√3tanα-1)(tanα-√3)=0∴tanα=√3/3或√3∵α为锐角∴α=30º或60º

由(sina-cosa)/(sina+2cosa)则:上下同时除以cosa得:(sina/cosa-1)/(sina/cosa+2)=(tana-1)/(tana+2)又tana=3则:(sina-c

sin^a-sinacosa-2cos^a=0(sina-2cosa)(sina+cosa)=0又a为锐角所以sina-2cosa=0sina=2cosatana=sina/cosa=2cosa/co

答案是二分之根号二,sin2a=2sinacosa,cos2a=cosa平方-sina平方

设tana=x,原方程化为x^2-(1+根号3）x+根号3=0.解得x=根号3或x=1,即tana=根号3或tana=1.因为a为锐角,所以a=60度或45度

cosAcosB-sinAsinB=sinAcosB-cosAsinBcosA(sinB+cosB)=sinA(sinB+cosB)因为B是锐角,所以sinB+cosB不等于0cosA=sinAtan

移项!sinA-cosA/sinA+cosA=1/33sinA-3cosA=sinA+cosA2sinA=4cosA∵tanA=sinA/cosA∴tanA=2

1.cos（A+B)=cosAcosB-sinAsinBsin（A-B)=sinAcosB-sinBcosAcosAcosB-sinAsinB=sinAcosB-sinBcosAcosA(cosB+s

tana+tanb=8tana*tanb=3tan(a+b)=(tana+tanb)/(1-tana*tanb)=8/-2=-4所以a+b>180cos(a+b)=-1/√17

tana=sina/cosa=1/2cosa=2sinasin^2a+cos^2a=1sin^2a+4sin^2a=1sin^2a=1/5sina=根号5/5cosa=2根号5/5

2tana+3sinb=74tana+6sinb=14tana-6sinb=1相加得5tana=15tana=3,cosa=(1/3)sina因为a是锐角,所以sina>0sin²a+cos

老师不讲或没讲到的题目就不该出这是误区,因为你们老师不是命题人!对于该题记住:sina/cosa=tana^o^

tan²A-√3tanA-tanA+√3=0(tanA-1)(tanA-√3)=0tanA=1或tanA=√3因为∠A为锐角所以∠A=45度或∠A=60度

α/2为锐角,tan(α/2)>0tan（α）=2tan(α/2)/{[1-tan(α/2)]^2}设tan(α/2)=xx^2+x-1=0x=(根号5)/2-1/2=tan(α/2)

a为锐角,且tana=2sina=2√5/5cosa=√5/5(sina-2)/(2cosa+sina)=(2√5/5-2)/(2√5/5+2√5/5)=(1-√5)/2

sin²a+cos²a=1sina=3分之2,且a是锐角cosa=√（1-sin²a）=√5/3tana=sina/cosa=2√5/5cota=1/tana=√5/2再

∵tanA+tanB+√3tanAtanB=根号3∴等式两边同÷根号3,得（tanA+tanB）/根号3+tanAtanB=1移项得（tanA+tanB）/根号3=1-tanAtanB,∴tanAta

sinA=12/13tanA=12/5

√3tan²A-4tanA+√3=0(√3tanA-1)(tanA-√3)=0tanA=√3/3或tanA=√3A=30°或A=60°

是(sina+cosa)/(sina-cosa)还是sina+cosa/sina-cosa无括号?是(sina+cosa)/(sina-cosa)的话=[(sina+cosa)/cosa]/[(sin