1.f(x)=sinx/4*√3cosx/4+cos^2x/4
=√3/2*sinx/2+1/2cosx/2+1/2
若f(x)=1,sin(x/2+30°)=1/2
cos(x+60°)=1-2sin^2(x/2+30°)=1/2
2.(2a-c)cosB=bcosC
2sinAcosB-sinCcosB=sinBcosC
2sinAcosB=sin(B+C)=sinA
cosB=1/2 B=60° A+C=120° 0°
1.f(x)=sinx/4*√3cosx/4+cos^2x/4
=√3/2*sinx/2+1/2cosx/2+1/2
若f(x)=1,sin(x/2+30°)=1/2
cos(x+60°)=1-2sin^2(x/2+30°)=1/2
2.(2a-c)cosB=bcosC
2sinAcosB-sinCcosB=sinBcosC
2sinAcosB=sin(B+C)=sinA
cosB=1/2 B=60° A+C=120° 0°