1. The problem statement, all variables and given/known data http://www.xtremepapers.com/Edexcel/Advanced%20Level/Mathematics/Subject%20Sorted/C3/Elmwood%20Papers/Elmwood%20B.pdf [Broken] Question 8(b) 2. Relevant equations 3. The attempt at a solution Ok so I found both values of dy/dx for BOTH EQUATIONS y = x2 - 4x → 2x - 4 y = |4x - x2| → |4 - 2x| could someone please claify this, I have never differentiated a modulus before Thus the two gradients of the lines are 4 and -4 BUT HOW DO I GO ON TO FIND THE angle between the tangents??