Let `a,b,c,d` be numbers in the interval `[0,pi]` such that `sina+7sinb=4(sinc+2sind), cosa+7cosb=4(cosc+2cosd)` Prove that `2 cos(a-d)=7 cos(b-c)`

If A+B+C=pi , prove that : sinA+sinB+sinC= 4cos( A/2 )cos( B/2) cos(C/2)

In triangleABC,A+B+C=pi ,show that sinA+sinB+sinC=4cos(A/2)cos(B/2)cos(C /2)

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

If A+B+C=pi , prove that : sinA+sinB+sinC= 4cos, A/2 cos, B/2 cos, C/2

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)) =

Prove that: sin(A+B)+cos(A-B)=(sinA+cosA)(sinB+cosB)

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 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 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_____