sinA+sinB+sinC=0,cosA+cosB+cosC=0,则cos(A-B)的值是多少?
sinA+sinB+sinC=0,cosA+cosB+cosC=0,则cos(A-B)的值是多少?
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)=______
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
已知sinA+sinB=sinC,cosA+cosB=cosC,求cos(A-B)的值
(1)已知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)
设A,B,C属于(0,90度),SINA+SINC=SINB,COSB+COSC=COSA,则B-A等于
sina+sinb+sinc=0 cosa+cosb+cosc=0求证cos*2a+cos*2b+cos*2c=3|2