
a cos x + b sinx
Hello
I would appreciate some help with the following question, which is, prove that:
If I do it like this:
I get:
I thought of doing it like this:
but then
So I can't seem to do it.
I did first have to show that:
, which I was able to do.
Any help would be very much appreciated,
Thank you

Re: a cos x + b sinx
Quote:
Originally Posted by
Furyan prove that:
Rewrite the righthand side using the formula .

Re: a cos x + b sinx
Why you do not try this,

Re: a cos x + b sinx

Re: a cos x + b sinx
Thank you both for taking the time to reply.
(There's nothing in the chapter I'm working through about either of the methods you have shown me, but I will study your posts in detail to see what I can learn from them.
Thank you very much for you efforts.)
Edit: Ah, actually there is an example showing how to determine which quadrant the angle is in. I never learnt that, I'm not sure how I got by without it. It seems pretty important, in fact, looking back it's one of the first things I should have learnt in trigonometry. (Doh)

Re: a cos x + b sinx
(Bow)Thank you,
(I will see if I can get:
just now seeing that is beyond me, but I guess I need to know that.)
Thank you very much indeed for your help. (Bow)
Edit: I think I understand now. Since and both and is in the second quadrant, . Thanks for pointing that out. I'm glad I know that now.(Happy)