For example, $0^{\circ}$ is $0$, $90^{\circ}$ is $1$, $180^{\circ}$ is $2$, $270^{\circ}$ is $3$, $360^{\circ}$ is $0$ (same as $0^{\circ}$), $450^{\circ}$ is $1$ (same as $90^{\circ}$).
Is the there are a formula to find out if both $90^{\circ}$ and $450^{\circ}$ is same and evaluate them to be $1$?
$360 $ degree is the full angle.
So if two angle $\theta$ and $\beta$ are given to you they are same if $\theta -\beta$ is an integral multiple of $360$
In other words $\theta -\beta$ should be divisible by $360$
In your case $450-90=360$ which is nothing but $1$ times $360$ so they are same.
$810-90=720$ and again it is divisible by $360$.
Imagine yourself moving on a circle. Your starting point is $0$ degree When you complete a full round you have covered 360 degrees. Now if you want to move 450 degrees you will have to move 90 degrees more. Where do you end up??
You end up 90 degree far from your starting point that was 0.
So 450 degrees and 90 degrees are equivalent on circle.