Error in the height of a flagpole

1. The problem statement, all variables and given/known data
An observer is 6m from the base of a flagpole. The angle of elevation of the top of the pole is measured as pi/3, with a possible error of 0.02 radians. Use the tangent line approximation to find the error in the calculated height of the pole.



2. Relevant equations
Tangent line approximation.



3. The attempt at a solution
My troubles here seem to be in setting up the proper equation. I started by drawing a right angle triangle, with the formula obtained from it being h=6tanx. I then took the derivative of this and plugged in pi/3 for x. Using pi/3, i then found a value for h, and set up the equation of the line. I then tried to plug 0.02 in for the x value in the line equation, and naturally this got me nowhere. The setup for this question is just stumping me entirely; I know how to use the tangent line approximation, so that is no problem, it's just finding out how to bring the 0.02 value into the solution. If anyone can be of help here I would appreciate it greatly, thanks.