1. The problem statement, all variables and given/known data A cat is standing 1m in front of a mirror. a virtual image is formed 10.0m behind the mirror. what is the radius of curvature for the mirror? 2. Relevant equations 1/f = (1/do)+(1/di) f=+/-(1/2)*R 3. The attempt at a solution (1/1m + 1/10m)^-1 = .909 .909*2 = 1.82 According to my answer key, R should be equal to 2.2m. the only way i get that answer is if i take (1/do)+(1/di) and not take its reciprocal...i would just plug it straight into the focal length equation to solve for R. Did he make a mistake??