(sinA-sinB)(sinA+sinB)推出sin(A+B)sin(A-B)
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(sinA-sinB)(sinA+sinB)推出sin(A+B)sin(A-B)
![(sinA-sinB)(sinA+sinB)推出sin(A+B)sin(A-B)](/uploads/image/z/19143366-6-6.jpg?t=%28sinA-sinB%29%28sinA%2BsinB%29%E6%8E%A8%E5%87%BAsin%28A%2BB%29sin%28A-B%29)
(sina-sinb)(sina+sinb)
=(sina)^2-(sinb)^2 (平方差公式)
=(1-cos2a)/2-(1-cos2b)/2 (二倍角公式)
=1/2*(cos2b-cos2a) (合并)
=1/2*{cos[(a+b)-(a-b)]-cos[(a+b)+(a-b)]} (化角 2a=(a+b)+(a-b) ,2b=(a+b)-(a-b))
=1/2*{[cos(a+b)cos(a-b)+sin(a+b)sin(a-b)]-[cos(a+b)cos(a-b)-sin(a+b)sin(a-b)]} (和角公式)
=1/2*2sin(a+b)sin(a-b) (合并)
=sin(a+b)sin(a-b) (约分)
=(sina)^2-(sinb)^2 (平方差公式)
=(1-cos2a)/2-(1-cos2b)/2 (二倍角公式)
=1/2*(cos2b-cos2a) (合并)
=1/2*{cos[(a+b)-(a-b)]-cos[(a+b)+(a-b)]} (化角 2a=(a+b)+(a-b) ,2b=(a+b)-(a-b))
=1/2*{[cos(a+b)cos(a-b)+sin(a+b)sin(a-b)]-[cos(a+b)cos(a-b)-sin(a+b)sin(a-b)]} (和角公式)
=1/2*2sin(a+b)sin(a-b) (合并)
=sin(a+b)sin(a-b) (约分)
sinA-sinB是否等于sin(A-B)
证明sin(a+b)sin(a-b)=(sina+sinb)(sina-sinb)
为什么sinA-sinB/sinA+sinB=cos[(A+B)/2]sin[(A-B)/2]/{sin[(A+B)/2
sinA+sinB=sin(A+B)是错误命题,
sinb/sina=cos(a+b),证明3sinb=sin(2a+b)
证明sin(2a+b)/sina-2cos(a+b)=sinb/sina
求证sin(2A+B)/sinA-2cos(A+B)=sinB/sinA
如何证明sin(A-B)*sin(A+B)=sinA²-sinB²
三角形ABC中,为什么sinA+sinB=2sin(A+B)/2*cos(A-B)/2
求证sina+sinb=2sin(a+b)/2*cos(a-b)/2
为什么sina+sinb==2sin(a+b)\/2*cos(a-b)\/2
如何证明sinA+sinB=2sin((A+B)/2)cos((A-B)/2)