sinA+sinB+sinc=0 cosA+cosB+cosC=0 cos(B-C)
来源：学生作业帮助网 编辑：六六作业网 时间：2024/07/11 15:01:03
sinA+sinB+sinc=0cosA+cosB+cosC=0cos(B-C)sinA+sinB+sinc=0cosA+cosB+cosC=0cos(B-C)sinA+sinB+sinc=0cosA
sinA+sinB+sinc=0 cosA+cosB+cosC=0 cos(B-C)
sinA+sinB+sinc=0 cosA+cosB+cosC=0 cos(B-C)
sinA+sinB+sinc=0 cosA+cosB+cosC=0 cos(B-C)
cos(B-C)=cosBcosC+sinBsinc又sinB+sinc=-sinA cosB+cosC=-cosA
所以同时平方sinB^2+sinc^2+2sinBsinc=sinA^2 cosB^2+cosc^2+2cosBcosC=cosA^2 两式相加 2（cosBcosC+sinBsinc）+2=1
cos(B-C)=cosBcosC+sinBsinc=-1/2
两个式子平方后相加即可
2sinc-sinb=sina cos c的最小值
sinA+sinB+sinC=0; cosA+cosB+cosC=0,求cos(B-C)的值?
sina+sinb+sinc=0,cosa+cosb+cosc=0,求cos(B-C)的值?
sinA+sinB+sinc=0 cosA+cosB+cosC=0 cos(B-C)
在△ABC中,求证：a(sinB-sinC)+b(sinC-sinA)+c(sinA-sinB)=0
sinA / cos(A/2) = sinB / cos(B/2) = sinC / cos(C/2)为什么等于sinA/2=sinB/2=sinC/2
已知cosA = cosθ×sinC,cosB = sinθ×sinc,求(sinA)^2+(sinB)^2+(sinC)^2的值
已知sinA+sinB+sinC=0,cosA+cosB+cosC=0,求cos(A－B)的值
已知sina+sinb+sinc=0且cosa+cosb+cosc=0 求cos(a-b)的值
已知sina+sinb+sinc=0,cosa+cosb+cosc=0,则cos(a-b)的值是?
sinA+sinB+sinC=0,cosA+cosB+cosC=o,则cos(A-B)=______帮帮忙
在三角形ABC中求证：a（sinB-sinC）+b（sinC-sinA）+c（sinA-sinB）=0
sina+sinb+sinc=0 cosa+cosb+cosc=0求证cos*2a+cos*2b+cos*2c=3|2
在△ABC中,sinA+sinB+sinC=0,cosA+cosB+cosC=0,求证：cos²A+cos²B+cos²C=3/2
在△ABC中,sinA+sinB+sinC=0,cosA+cosB+cosC=0.求证：cos²A+cos²B+cos²c=3／2.
已知sinA+sinB=sinC,cosA+cosB=cosC,求cos(A-B)的值
已知sinA+sinB=sinC,cosA+cosB=cosC,求cos(A-B)的值
cos (A/2)=2sin[(C-B)/2],求证sinC-sinB=1/2sinA