1. The problem statement, all variables and given/known data cosx=12/13 3pi/2 is less than or equal to x is less than or equal to 2pi 2. Relevant equations sin2x = 2sinxcosx cos2x = 1-2(sinx)^2 tan2x = (2tanx)/(1-(tanx)^2) 3. The attempt at a solution Using the tan2x formula, I get -60/47. Using the sin2x (sin2x=-120/169) and cos2x (cos2x=119/169) formulas, than dividing sin2x by cos2x, I get -120/119. tan2x=2(-5/12)/(1-2(-5/12)^2) =(-10/12)/47/72 =-60/47 Why am I getting different values?