Hi /sci/

I'm a retard and don't know how to word this properly to find on the internet so I figured I'd come here. I'm a /fit/izen and today was doing leg extensions and pondered to myself, "If the stack of weights on the leg extension moves X-amount of inches, what is the radial distance traveled given a known length of the radius (let's say my shins are 1.5 feet) and a known amount of degrees?" Basically, if my 1.5 foot shin traveled in an arc 90 degrees, what is the linear distance the weight stack would move upwards?

I really appreciate your help. I've been puzzled over this all day. I'm no math whiz. Pic not related but I figured I'd share some gee-whiz.