Edexcel A2 C4 Mathematics June 2016 - Official Thread

Isn't that from the IAL paper? that trig application question?

I've never really understood why when they say that 'the tangent to the curve at Q is parallel to the y-axis.'. you have to make the denominator equal to zero. (this is after you have found dy/dx).

Can someone please explain to me why this is so because i just cant seem to visualise it. Thanks

I've never really understood why when they say that 'the tangent to the curve at Q is parallel to the y-axis.'. you have to make the denominator equal to zero. (this is after you have found dy/dx).

Can someone please explain to me why this is so because i just cant seem to visualise it. Thanks

Crash course of vectors!
https://www.youtube.com/watch?v=4RglgO93VfM

A little might be missed out but enough to get started on Past papers!

Guys I have a quick qs on C34 june 2014 IAL : aka @Zacken

Qs. 6b if we're finding a general solution for a differential equation, why does it matter if I sub in boundary conditions in y = f(x) form to find C instead of leaving it in ln form?

You see if I leave it in y form and find C I get 35/9, but the mark scheme solved C in ln form and got ln(36) Ultimately the final answer aka the y=f(x) form for the particular solution is different...

my answer = y = (2x-1) / (x+1)^3 + 35/9

mark scheme = y = 36(2x-1) / (x+1)^3

Can someone explain why I need to leave it in ln form to find C and why it affects the final answer thanks. Appreciate it! x

@SeanFM Do you have a solid method for answering questions like part bii of this?

Nothing really special.. just find where sin(theta-alpha) = 1, (pay attention to the range) that's where the maximum will be.

Ah okay, thanks What do you mean by pay attention the range?

Choose the right value of theta then you're solving sinx = 1 where x = theta - alpha.

Oh okay so using 2theta etc. when the question had (2theta - a)?

Just stuff like that when you're trying to solve trig equations, yes.

If tangent is paralel to y it means the gradient is straight up...so dy/dx has to equal infinite, in fractions x/0 equals infintie

Haven't really thought about it before in the terms you describe, but the reason is that a line parallel to the y-axis has an infinite gradient, and this is the same as dividing by 0 (it also means that the normal has 0 gradient)
hope this helps

Thanks ! what if they said that the tangent is parallel to the x-axis. that's infinite as well. so surely we must equal the numerator to zero right?

I'm not sure, but are you 100% sure that you've done it right for your method?

Connected rates of change are often similar types of question. Ideas include:
Think what the 3 differentials in your equation must be
Use units from the question to help you
Think what basic shape info you need to create your missing differential

Please put up a question you don't like for us to look at

Thanks for helping! Heres an example (part b):