I got another one, its been blaggin my head...

Say i have an arc on a surface and I need to find its distance from one end to another. My arc distance will be called X

I also have a radius which is 12.5

X= 2 PI x R = ??? / 8 (45deg)
X= 6.28 x 12.5= 78.53/8 = 9.81

Now I know thats the correct measurement for X..

But there’s a problem with this method, what if the angle has to be different to 45 degrees. Is going to screw the formula up because I won’t be able to divide it by 8

So the correct formula is....

angle x 2PI Radius = Answer in radians? which is divided by 360

X = 45 x 2 x PI x 12.5 = 3534.29 / 360 = 9.8174

But this formula is used because? i cant word it. Is it something to do with radians and degree's. The 2nd formula works because its not working it out using radians and just degree's? My head hurts