已知cosA = cosθ×sinC,cosB = sinθ×sinc,求(sinA)^2+(sinB)^2+(sinC

来源：学生作业帮编辑：作业帮分类：数学作业时间：2024/09/02 05:19:05

已知cosA = cosθ×sinC,cosB = sinθ×sinc,求(sinA)^2+(sinB)^2+(sinC)^2的值

cosA = cosθ×sinC ∴(cosA )^2= cos²θ×sin²C
∴(sinA)^2=1-(cosA )^2=1- cos²θ×sin²C
同理(sinB)^2=1-sin²θ×sin²C
∴(sinA)^2+(sinB)^2+(sinC)^2
=1- cos²θ×sin²C+1-sin²θ×sin²C+(sinC)^2
=2-(sinC)^2[1-sin²θ-cos²θ]
=2-(sinC)^2*0
=2

已知sinA+sinB=sinC,cosA+cosB=cosC,求cos(A-B)的值 cosa+cosb+cosc=sina+sinb+sinc=0 求（cosa)^2+（cosb)^2+（cosc)^2 sinA+sinB+sinC>=cosA+cosB+cosC 三角函数已知sinA+sinB+sinC=0 cosA+cosB+cosC=0 求（cosA）^2+（cosB）^2 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? 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 (1)已知sinA+sinB+sinC=0,cosA+cosB+cosC=0.求cos(B-C)的值. 已知 A+B+C=π,sinA+sinB+sinC=cosA+cosB+cosC.求 ( cos2A+cos2B+cos 已知（cosA+2cosC)/（cosA+2cosB)=(sinB/sinC)求三角形ABC形状三角形ABC中,已知sinC=(sinA+sinB)/(cosA+cosB),求C