Expression 3: "P" left parenthesis, "R" , "A" , "t" , right parenthesis equals left parenthesis, "R" cos "A" plus "R" Subscript, 2 , Baseline cos "t" , "R" sin "A" plus "R" Subscript, 2 , Baseline sin "t" , right parenthesisPR,A,t=RcosA+R2cost,RsinA+R2sint