If `(ad -bd)/(a-b-c+d) =(ac-bd)/(a-b-d+c)`, then show that each ratio is equal to `(a+b+c+d)/4`.

If (sin (x+y))/( sin(x-y))=(a+b)/(a-b) , then (tan x)/( tan y) is equal to .............. A) b/a B) a/b C) ab D) a-b

If a, b and c are non-coplanar vectors and d=lambdaa+mub+nuc , then lambda is equal to: a) ([dbc])/([bac]) b) ([bcd])/([bca]) c) ([bdc])/([abc]) d) ([cbd])/([abc])

Write the Power set of the set A = {a, b, c, d}

If ( cos (A+B))/( cos (A-B)) =( sin (C+D))/( sin (C -D)) then prove that tan A tan B tan C + tan D=0 ................. A) 0 B) -1 C) sqrt3 D) 1

If t a n A+cot A=4, then tan^4A+cot^4A is equal to............ a. 110 b. 191 c. 80 d. 194