got exams coming up in 8 days... need help with this one particular question on c3 can anyone tell me what happens in between step 2 and 3 in the mark scheme (which is underneath)? what happens to the e's and how do you get tan from sec? i know there are a few fellow mathematicians that can help... thanks

I can answer one part of it for you Sec=1/cos and, of course, tan=sin/cos. So that will give 1+tan(squared)u=Sec(squared)u You should be able to google these rules. When you differentiate using dy/dx=0 the e elements of the equation cancel each other out. As 1+tan(squared)x = Sec(squared)x, thats a simple substitution. Then you can simplify the equation and solve for Tan x. Stick to the rules for working out circumferences of a circle and never forget the relationship of tan, sin and cos. Got me through my maths exams......but that was 20 years ago. I'm getting rusty in my old age. Hope that helps

Step from line 2 to 3 is dividing through by e^(2x), then using trig identity sec2 x = tan2 x + 1 Next step is factorisation. Next step is square rooting both sides and re-arranging.

You can only divide through by e^2x and ignore it as a solution because it can never be zero, it's an important point