Suppose that 'a' is a non-zero real number for which `sin x+sin y=a and cos x + cos y= 2a`. The value of `cos(x-y) is`

If sin x + sin y = a, cos x + cos y = b, then what is the value of cos (x-y) ?

If sin x + sin y =a and cos x+cos y = b , find the values of : tan frac (x-y)(2) .

If cos x + cos y =2, then value of sin x + sin y is

If cos x + cos y = 2, "then the value of" sin(x + y) is-

If sin x + sin y =a and cos x+cos y = b , find the values of : tan frac (x+y)(2) .

If cos x + cos y =2 , then the value of sinx + sin y is

If (sin x) (sin y) = 1, then (cos x) (cos y) =?

Let x and y be real numbers such that (sin x)/(sin y)=3 and (cos x)/(cos y)=(1)/(2). The value of (sin2x)/(sin2y)+(cos2x)/(cos2y) is (i)(49)/(58)(ii)(41)/(58)(iii)(51)/(58)( iv) none of these