在三角形ABC中已知sinAcosC+sinCcosA-2sinBcosB=0 (1)求B的值(2)已知角A=派/6.求2SIN^2A+C...在三角形ABC中已知sinAcosC+sinCcosA-2sinBcosB=0 (1)求B的值(2)已知角A=派/6.求2SIN^2A+COS(A-C)的值高一〈已知派/4
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![在三角形ABC中已知sinAcosC+sinCcosA-2sinBcosB=0 (1)求B的值(2)已知角A=派/6.求2SIN^2A+C...在三角形ABC中已知sinAcosC+sinCcosA-2sinBcosB=0 (1)求B的值(2)已知角A=派/6.求2SIN^2A+COS(A-C)的值高一〈已知派/4](/uploads/image/z/14578943-23-3.jpg?t=%E5%9C%A8%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E4%B8%AD%E5%B7%B2%E7%9F%A5sinAcosC%2BsinCcosA-2sinBcosB%3D0+%281%29%E6%B1%82B%E7%9A%84%E5%80%BC%282%29%E5%B7%B2%E7%9F%A5%E8%A7%92A%3D%E6%B4%BE%2F6.%E6%B1%822SIN%5E2A%2BC...%E5%9C%A8%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E4%B8%AD%E5%B7%B2%E7%9F%A5sinAcosC%2BsinCcosA-2sinBcosB%3D0+%281%29%E6%B1%82B%E7%9A%84%E5%80%BC%282%29%E5%B7%B2%E7%9F%A5%E8%A7%92A%3D%E6%B4%BE%2F6.%E6%B1%822SIN%5E2A%2BCOS%28A-C%29%E7%9A%84%E5%80%BC%E9%AB%98%E4%B8%80%E3%80%88%E5%B7%B2%E7%9F%A5%E6%B4%BE%2F4)
在三角形ABC中已知sinAcosC+sinCcosA-2sinBcosB=0 (1)求B的值(2)已知角A=派/6.求2SIN^2A+C...在三角形ABC中已知sinAcosC+sinCcosA-2sinBcosB=0 (1)求B的值(2)已知角A=派/6.求2SIN^2A+COS(A-C)的值高一〈已知派/4
在三角形ABC中已知sinAcosC+sinCcosA-2sinBcosB=0 (1)求B的值(2)已知角A=派/6.求2SIN^2A+C...
在三角形ABC中已知sinAcosC+sinCcosA-2sinBcosB=0 (1)求B的值(2)已知角A=派/6.求2SIN^2A+COS(A-C)的值
高一〈已知派/4
在三角形ABC中已知sinAcosC+sinCcosA-2sinBcosB=0 (1)求B的值(2)已知角A=派/6.求2SIN^2A+C...在三角形ABC中已知sinAcosC+sinCcosA-2sinBcosB=0 (1)求B的值(2)已知角A=派/6.求2SIN^2A+COS(A-C)的值高一〈已知派/4
sinAcosC+sinCcosA-2sinBcosB=0
sin(A+C)-sin(2B)=0
sin(180°-B)-sin(2B)=0
sinB=sin(2B)
∵B≠2B
∴B=180°-2B
B=60°
A=π/6=30°
C=180°-60°-30°=90°
2SIN^2A+COS(A-C)
=2*(1/2)^2-1/2
=0
sinAcosC+sinCcosA-2sinBcosB=0
sin(A+C)-sin2B=0
sinB-sin2B=0
sinB(1-2cosB)=0
1-2cosB=0
cosB=1/2
B=60°
A=派/6.
C=90
2SIN^2A+COS(A-C)
=1/2-1/2
=3/2