1、sin(2x+B)/sinx - 2cos(x+B)=sinB/sinx2、sinx+sinB)^2 + (cosx+cosB)^2=4cos^2*x-B/2

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1、sin(2x+B)/sinx-2cos(x+B)=sinB/sinx2、sinx+sinB)^2+(cosx+cosB)^2=4cos^2*x-B/21、sin(2x+B)/sinx-2cos(x

1、sin(2x+B)/sinx - 2cos(x+B)=sinB/sinx2、sinx+sinB)^2 + (cosx+cosB)^2=4cos^2*x-B/2
1、sin(2x+B)/sinx - 2cos(x+B)=sinB/sinx
2、sinx+sinB)^2 + (cosx+cosB)^2=4cos^2*x-B/2

1、sin(2x+B)/sinx - 2cos(x+B)=sinB/sinx2、sinx+sinB)^2 + (cosx+cosB)^2=4cos^2*x-B/2
1.左边=[sinx*cos(x+b)+cosx*sin(x+b)]/sinx-2cos(x+b)
=cos(x+b)+[cosx*sin(x+b)]/sinx-2cos(x+b)
=[cosx*sin(x+b)]/sinx-cos(x+b)
=[cosx*sin(x+b)-2sinx*cos(x+b)]/sinx
={sin[(x+b)-x}/sinx
=sinb/sinx=右边.
2.左边=(sinx+sinB)^2 + (cosx+cosB)^2
=(sinx)^2+2sinx*sinb+(sinb)^2+(cosx)^2+2cosx*cosb+(cosb)^2
=2+2cos(x-b)
=4{cos[(x-B)/2 ]}^2=右边.