Stuck on this one question.

3cosx + 4sinx, write in terms of t=tan x/2

The answer is 3 - 3t^2 +8t / 1+t^2

Sorry I just wrote it in normal text, in a hurry lol.

Thanks

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- Mar 3rd 2010, 10:28 PMicesta1Writing expression in terms of t=tan x/2
Stuck on this one question.

3cosx + 4sinx, write in terms of t=tan x/2

The answer is 3 - 3t^2 +8t / 1+t^2

Sorry I just wrote it in normal text, in a hurry lol.

Thanks - Mar 3rd 2010, 10:42 PMGrandad
Hello icesta1Provided you know the formulae:

$\displaystyle \sin x = \frac{2t}{1+t^2}$ and $\displaystyle \cos x = \frac{1-t^2}{1+t^2}$I don't see what the problem is. Just substitute these into the expression, and the answer follows immediately:$\displaystyle 3\cos x +4\sin x = \frac{3(1-t^2)}{1+t^2}+ \frac{8t}{1+t^2}$Have you seen these formulae before?$\displaystyle =\frac{3-3t^2+8t}{1+t^2}$

Grandad - Mar 3rd 2010, 11:12 PMicesta1
Hm... its funny cause I actually have that written in my book lol. I think i might have been looking at the wrong answer while doing it >_< lol.

Thanks anyways :)

EDIT: Nvm i got it