Normals

I have just got 100% on my equations of normals activity, I'm pleased about that! I knew what a normal is from Standard Grade Physics, but I never knew how to find the equation of one, until yesterday. It's similar to finding the equation of a tangent: you differentiate the given curve's equation, then substitute in the associated x value to find the gradient of the tangent, then take the negative reciprocal, to find the normal's gradient (it is perpendicular to the tangent). You then substitute the x value into the original equation to find a y value, then use y-b=m(x-a) and rearrange for the equation of the normal. It sounds complicated, but it's multiple choice, and on at least 4 questions out of 10 today, Mathletics didn't find the perpendicular gradient and used the tangent's gradient in the equation instead. So that's that finished, and I only need to do the co ordinate geometry test now!