x+y=1,4x-y=4quad " nl "quad cos9/100

I : If cos x + cos y=1/3 , sin x+sin y=1//4 " then " cos (x+y)=7//25 II : If cos x + cos y=1//3 , sin x + sin y=1//4 " then " sin(x+y)=24//25

If cos x+ cos y = 1//3 , sin x + sin y=1//4 " then " cos (x+y)=

If the lines of regression of y on x is y=x/4 and x on y is x=y/9 +1 , then the value of r is

If sin x cos y=(1)/(4) and 3tan x=4tan y then sin(x-y)=

If sin x cos y=(1)/(4) and 3tan x=4tan y then sin(x-y)=

Solve : (3)/(x + y ) + ( 2)/(x - y ) = 2 and (9)/(x + y ) - ( 4)/(x - y) = 1 .

If cos x+cos y=1 and cos x cos y=(1)/(4) then the G.S are