A function `f(theta)` is defined as : `f(theta) = 1 - theta+(theta^2)/(2!) - (theta^3)/(3!) +(theta^4)/(4!)….` why is it necessary for `theta` to be a dimensionless quantity ?

Explanation

`Here, f(theta) = 1 +(theta^2)/(2!) - (theta^3)/(3!)+ (theta^4)/(4!) - …… .`
As `f(theta)` is sum of different powers of `theta,` therefore `theta` must be dimensionless. This is because quantities having different dimensions cannot be added.