text: tan(x + (pi/2)) = -cotx? prove this identity and show all steps. tan(x+pi/2)=sin(x+pi/2) / cos(x+pi/2)  sin(x+pi/2)=sinx cos(pi/2) + sin(pi/2) cosx= cosx cos(x+pi/2)=cosx cos(pi/2) - sin(pi/2)sinx= -sinx plug these two results to the above formula, you have  tan(x+pi/2)=cosx/(-sinx)= -cotgx