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<=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

Single Choice Questions: 1.Let 0<=alpha, beta, gamma, delta,<=pi where beta and gamma are not complementary such that 2cos alpha+ 6 cos beta+7 cos gamma+9 cos delta=0 and 2 sin alpha- 6 sin beta+7 sin gamma-9 sin delta=0 ifcos(alpha+delta)/cos(beta+gamma)=m/nwhen m and n are relatively prime positive numbers, then the value of (m+n) is equal to (A)11 (B)10 (C)9 (D)7

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 :

In any quadrilateral ABCD, show that: cosA cosB-cosC cosD="sin"A "sin"B-"sin"C "sin"D.

Find the value of (2^0 + 4^0)/7^0 a)2 b)0 c)9 d) 6/7

If A, B, C, D be the angles of acyclic quadrilateral, show that : cosA +cosB+cosC+cosD=0 .

If A+B+C= pi/2 , show that : cos^2 A + cos^2 B + cos^2 C = 2 + 2 sinA sinB sinC .

Let A , B , C be the three angles such that A+B+C=pi . If T a nAtanB=2, then find the value of (cos(A-B))/(cosC)