[Loz17]

yarrrp thank goodness...

[Inquilaab]

Is there an easy way of solving those trig identities questions in C2?! the book just confused me more

[EvenStevens]

Just know that

And you can rearrange that for and

It just takes practise.

[Kyalimers]

Trig feels piss, especially when you start integrating it in C4

[Horizontal 8]

Sketch the curve with equation showing the coordinates of any points where the curve cross the coordinate axes.

Also according to the mark scheme it crosses the x-axis at x=1, x=3 and x=-1. I expanded then factorised which works but isn't factorising cubics meant to be C2 (for Edexcel) and this is C1...Is there any other way?

Any help would be appreciated.

[Kyalimers]

how many marks is it?

[Horizontal 8]

3 marks

[Kyalimers]

well you can get that x=1 and -1 easily by making the brackets = 0

Then work from there.

[EvenStevens]

I thought cubic factorisation cropped up in C1 sometimes as well...

[8inchestall]

(Original post by sohanshah)
well you can get that x=1 and -1 easily by making the brackets = 0

Then work from there.

I have a problem,and it's to do with the cosine rule
i know the rule is
So in order to find cosA
i do


however this always gives me a minus value and sometimes not the right angle. How come it always gives me the wrong value, have i done something wrong here?
the question i am stuck on is May 07 question 4(a)

[EvenStevens]

Ugh, June 05 is such a horrible C1 paper.

It's not hard... just most of the values are fractions and horrible numbers like that. You waste most of your time multiplying, subtracting and adding fractions together.

[Loz17]

CosA= b^2 +c^2-a^2/2bc

And as i recall if you literakky plug those values in and simplify without actually dividing, you'll get 30/45 which is equal to 3/4

also if the cosine rule is wrong can someone tell me please and sorry for lack of latex, cant use it!

And a hint for b), think about trig identities!

[EvenStevens]

To 8inchestall, use the inverted cosine rule...

[8inchestall]

ahh cheers, i get it now. simple mistake of moving all values to the wrong side i guess.

[8inchestall]

(Original post by 8inchestall)
ahh cheers, i get it now. simple mistake of moving all values to the wrong side i guess.

do and

or is the latter wrong?

[EvenStevens]

No,

It never = 1.

[Kyalimers]

(Original post by 8inchestall)
do and

or is the latter wrong?

the latter is most definitely wrong.

[Loz17]

Use sin^2x+cos^2=1, put in the value of cos from a) and solve for sin

[EvenStevens]

If it helps, .

<_<

[8inchestall]

(Original post by EvenStevens)
If it helps, .

<_<

no need to get cocky, i was just checking to see i had the right stuff written down.