If `f(x)=sinx+cosa x` is a periodic function, show that `a` is a rational number

If f(x) = sinx + cos ax is a periodic function then a cannot be

If f(x) is a periodic function with period T, then

If f(x)=cos x+cos ax is periodic function, then a must be (a)an integer (b) a rational number (c)an irrational number (d) an even number

The function f(x)=|sin4x|+|cos2x| is a periodic function with period

If f(x) is a continuous function such that its value AA x in R is a rational number and f(1)+f(2)=6 , then the value of f(3) is equal to

If f(x) is periodic function with period, T, then

f(x) = e^(sinx+cosx) is an increasing function in

If f(x) is an odd periodic function with period 2 ,then f(4)=