Auxilary Method

[frog1944]

Hi,

For the auxiliary method, when it asks me to find say, sinx + cosx = rsin(x+ y), I usually just use the fact that r^2 = a^2 + b^2, and that tan(y) = b/a, and then just plug and chug. However, some worked solutions I've seen for trials and friends who do the method, they expand the RHS and equate like terms. If I do it my way will I lose marks?

Thanks

[RuiAce]

I think Jake always just used the formula

[frog1944]

Ok, so I shouldn't lose marks for using the formula? When would I not be allowed to use the formula (Probably prove that sinx + cosx = ...)?

[RuiAce]

If they ask you to prove it then you most certainly cannot, because you're assuming what you're trying to prove.

As far as I know of, it should be safe when you're just trying to apply it.

[frog1944]

Awesome! Thanks RuiAce