Hello icesta1 Originally Posted by
icesta1 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
Provided 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}$$\displaystyle =\frac{3-3t^2+8t}{1+t^2}$
Have you seen these formulae before?
Grandad