Edexcel A2 C4 Mathematics June 2016 - Official Thread

What part of trigonometry are you struggling with?

If it's spotting the identities then you're going to want to go over them again and do a lot of problems involving them (if you get bored try some trig. integrals)

If it's just general solving, perhaps review what the sine, cosine and tangent formulae do so that you have a better understanding of exactly what you're doing when evaluating

$\tan(x-53)=\cot(x+35)$ where $0\leq x \leq360$

What part of trigonometry are you struggling with?

If it's spotting the identities then you're going to want to go over them again and do a lot of problems involving them (if you get bored try some trig. integrals)

If it's just general solving, perhaps review what the sine, cosine and tangent formulae do so that you have a better understanding of exactly what you're doing when evaluating

edit: There was a good trig problem posted by @13 1 20 8 42 somewhere I believe, it ran something like this:

$\tan(x-53)=\cot(x+35)$ where $0\leq x \leq360$

Isn't that elementary?

$\tan \left(\frac{\pi}{2} - x\right) = \cot x$ so $\cot (x + 35^{\circ}) = \tan (55^{\circ} - x)$, hence your equation is nothing but:

$\tan (x - 53^{\circ}) = \tan (55^{\circ} - x)$ whereupon a standard comparing of arguments and adding $\pi$ because periodicity gets you your solutions? Seems too easy for C3 trig, no?

Seems about the level of C3 trig tbh, not like C3 trig is particularly difficult
Isn't cot introduced at C3...I'd say otherwise it is more C2 style I guess.
The first identity used there is one I doubt everyone will automatically know doing C3 also.

Isn't that elementary?

$\tan (x - 53^{\circ}) = \tan (55^{\circ} - x)$ whereupon a standard comparing of arguments and adding $\pi$ because periodicity gets you your solutions? Seems too easy for C3 trig, no?

...

Fair enough. I love finding shortcuts that turn 8 mark A-Level questions into a 2 lined answer that gets the examiner ripping out their hair.

Yeah, identities and not making stupid mistakes when solving trig equations (i.e. remembering when values are negative/positive, forgetting about domains etc). I'll just have to work a bit harder at trig questions I guess.

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If you have seen the associated STEP question (I think that is where I recalled this idea from anyway..), this will be too easy..but otherwise a nice test of your "feel" for trig derivatives/integrals. Think the hint was given in the STEP question, but it makes things a bit trivial so it can be optional..

Find $\displaystyle \int\frac{cosx}{cosx+sinx}dx$
Hint:

If you have seen the associated STEP question (I think that is where I recalled this idea from anyway..), this will be too easy..but otherwise a nice test of your "feel" for trig derivatives/integrals. Think the hint was given in the STEP question, but it makes things a bit trivial so it can be optional..

Find $\displaystyle \int\frac{cosx}{cosx+sinx}dx$
Hint:

This is a favourite of mine:

$\displaystyle \int_{-1}^{1} \frac{\mathrm{d}x}{x^2}$

Oooh ln x^2!!!!

omg yas!!! genius

No but seriously your clever addition of zeroes is genius. I'm just wondering how the heck you spot it

I posted this a few days ago, if you want - another way of doing it is:

This is a favourite of mine:

$\displaystyle \int_{-1}^{1} \frac{\mathrm{d}x}{x^2}$

I feel like a fool because I tried this, had to ignore some $\ln(-1)$ terms (bad maths I know) and got $\frac{4}{3}$ only to check on WolframAlpha that the integral doesn't converge...