Notice what, exactly. I still don’t get it.

Notice what??

Yeah, dividing a circle into 360 parts, then subdividing those by 60, and further subdividing those by 60 makes so much more sense than just using ratio of a number fundamental to circles themselves.

SOH CAH TOA is just a trick to make rote memorization of procedure easier. Understanding the unit circle will let you understand what trigonometry is actually doing.

for the same reason that rulers start with 1, it would be utterly pointless to use anything else.

Any circle could have its radius technically be 1, as long as you set the units of measurement so that 1 equals the radius of the circle.

Because it’s a unit circle.

It was freely chosen for simplicity.

If you choose another R, the other sides (x and y) become R*cos(th) and R*sin(th)

I don’t understand what is harmful about the unity circle either.