" If "f(y)=log y," then "f(y)+f((1)/(y))" is equal to "

If f(x)+f(y)=f((x+y)/(1-xy)) and f'(0)=3, then f(tan((1)/(3))) must be equals to

If f(x) = cos(log x) , then f((1)/(x)) f((1)/(y) - (1)/(2)[f((x)/(y)) + f(xy)] =

A mapping f is defined : f:(x,y)rarr (x+y,x-y) then f(-1,-2) is equal to

Let f be a function satisfying f(x+y)=f(x) *f(y) for all x,y, in R. If f (1) =3 then sum_(r=1)^(n) f (r) is equal to

If f(x)=cos(log x), " then " f(x)*f(y)-(1)/(2)[f((x)/(y))+f(xy)] has the value

If f(x)=cos((log)_e x),\ t h e n\ f(1/x)f(1/y)-1/2{f(x y)+f(x/y)} is equal to a. "cos"(x-y) b. log(cos(x-y)) c. 0 d. "cos"(x+y)

If f(x)=cos(log x), then f(x)f(y)-(1)/(2)[f((x)/(y))+f(xy)]=

If f(x)=cos(log x), then f(x)f(y)-(1)/(2)[f((x)/(y))+f(xy)]=