Let `0lt=a , b , c ,dlt=pi,` where b and c are not complementary, such that `2cosa+6cosb+7cosc+9cosd=0` and `2sina-6sinb+7sinc-9sind=0,` then the value of `3(cos(a+d))/("cos"(b+c))` is_____

Let 0 le a,b,c,d le pi where b,c are not complementary such that 2cosa + 6cos b + 7cosc + 9cosd = 0 and 2sina-6sinb + 7 sinc-9sind=0 .Then the value of (cos(a+d))/(cos(b+c)) =

If a, b, c, d in (0, pi) and b+c ne pi/2 such that 2cosa+6cosb+7cosc+9cosd=0 and 2sina-6sinb+7sinc-9sind=0, then the value of (3cos(a+d))/cos(b+c) is

Let 0<=a,b,c,d<=pi, where b and c are not complementary,such that 2cos a+6cos b+7cos c+9cos d=0 and 2sin a-6sin b+7sin c-9sin d=0, then 2sin a-6sin b+7sin c-9sin d=0, then the value of 3(cos(a+d))/(cos(b+c)) is

Let 0<=a,b,c,d<=pi where b and c are not complementary such that 2cos a+6cos b+7cos c+9cos d=0 and 2sin a-6sin b+7sin c-9sin d=0 Then 2sin a-6sin b+7sin c-9sin d=0 Then the value of (cos(a+d))/(cos(b+c)) is

If sinA+sinB=C,cosA+cosB=D , then the value of sin(A+B) =

If sinA+sinB=c,cosA+cosB=D, then the value of sin(A+B)=

If cosA+cosB+cosC=0,sinA+sinB+sinC=0andA+B+C=180^(@) then the value of cos3A+cos3B+cos3C is :

If cosA+cosB+cosC=0,sinA+sinB+sinC=0andA+B+C=180^(@) then the value of cos3A+cos3B+cos3C is :