化简 sin(a B)-2sinacosb
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倍角公式熟悉吗?再答:再问:叶知秋??再答:小说看多了吧再问:我看你头像再答:?再问:再问:求解!!!应该不是很难
tanc=sinc/cosc=(sinA+sinB)/(cosA+cosB)左分子乘右分母等于右分子乘左分母,并移项得sinAcosC-sinCcosA=sinCcosB-sinBcosC即sin(A
[sin(2A+B)]/sinA-2cos(A+B)=[sin(A+B+A)]/sinA-2cos(A+B)=[sin(A+B)cosA+cos(A+B)sinA]/sinA-2cos(A+B)=[s
三角形的顶点一般用大写字母BC=√5,AC=3,sinC=2sinA(1)利用正弦定理sinA:sinC=BC:AB∴AB=BC*sinC/sinA=√5*2=2√5(2)利用余弦定理cosA=(AB
由正弦定理a/sinA=b/sinB=c/sinCsinA+sinB=√2sinC所以a+b=√2ca+b+c=2√2+2所以√2c+c=2√2+2所以AB=c=2a+b=√2c=2√2S=1/2ab
因为2π/3在Y轴负半轴上,则2π/3-a在第3象限上则sin(2π/3-a)=-cosa1-sin(2π/3-a)/sina=1+cosa/sina=1+cota
不等再问:等于多少再答:应该是-sin(a)再问:应该……再答:绝对
诱导公式:sin(a-2π)=sina,sin(π+a)=-sina也可以画图看:sin就是角对应射线在半径为1的圆上交点的纵坐标-2π就是把角顺时针转一圈,还是原位置,sin不变+π是逆时针转半圈,
我来第一题吧3(sina+cosa)^4+6(sina-cosa)^2+4(sin^6a+cos^6a)=3(sina+cosa)^2*(sina+cosa)^2+6(sin^2a+cos^2a-2s
Sin^4a+Sina*Cosa+Cos^2a=(sin^2a)^2+1/2sin2a+1/2(1+cos2a)=[(1-cos2a)/2]^2+1/2sin2a+1/2cos2a+1/2=1/4(1
(1+sina+cosa)[sin(a/2)-cos(a/2)]/√(2+2cosa)=(2sina/2*cosa/2+2cos^2a/2)[sin(a/2)-cos(a/2)]/√(2+4cos^2
[sin(60+a)+cos120*sina]/cosa=[sin60cosa+cos60sina+cos120sina]/cosa=[√3/2cosa+1/2sina-1/2sina]/cosa=√
sinA+sin(A+2/3π)+cos(A+5/6π)=sina+sinacos2/3pai+sin2/3paicosa+cosacos5/6pai-sinasin5/6pai=sina-1/2si
sinA/(1+sinA)-sin/(1-sinA)=[sinA(1-sinA)-sinA(1+sinA)]/[(1+sinA)(1-sinA)]=-2sin^2A/cos^2A=-tan^2A
∵a*b=cosa*cosb-sina*sinb=cos(a+b)=1/2∵a,b为锐角∴a+b0∴sin(a+b)=√1-cos²(a+b)=√(1-1/4)=√3/2
sin=sinAcosB+cosAsinB=根号2/2(sinA+sinB)cosB=cosA=根号2/2A=B=45°边长b=c=根号2/2ab=c=2a=2根号2
sin^2a*tana+cos^2*cota+2sina*cosa=sin^2a*sina/cosa+cos^2a*cosa/sina+2sina*cosa=(sin^4a+cos^4a)/sina*
sin^2a*tana+cos^2a/tana+2sina*cosa=(1-cos^2a)*tana+(1-sin^2a)/tana+2sina*cosa=tana-sina*cosa+1/tana-