Is it just me or is this question incorrect? (1 Viewer)

[5647382910]

The question is question 6) b) ii) of the 2008 HSC: http://www.boardofstudies.nsw.edu.a...s/pdf_doc/2008HSC-mathematics-extension-2.pdf

Using the perpendicular distance formula you get

SR =

But the question states that [Edit... the numerator should read ab(esec(theta) -1)]
SR =

and the MANSW book has a solution that states that since a>0, b>0, e>0 and sec(theta)>1, e sec(theta) - 1 > 0, thus the absolute signs are removed.

My problem with the Q is that sec(theta) is not > 1, since theta is defined from -pi to pi, therefore you cant assume that what is in the absolute signs is +ve.

Am i wrong???.... someone please help this is for an assignment....
BTW, i think terry lee may have realised this too http://www.hsccoaching.com/Resources/2008Ext2.pdf

Thanks in advance

 

[Timothy.Siu]

i think you are right, but the question just asks to Show that that is true

if i had a question x^2+2x-3=0
i could say
Show that x=-3
(even though x=1 as well)
thats just what i think

 

[5647382910]

ye... i get what ur saying,
but the answer or proof to this question involves an incorrect statement, namely sec(theta) > 1; Do you think i should just go with the flow and write this down for my assingment???

 

[Timothy.Siu]

yeah i see, i dunno what to do then lol

 

[Trebla]

It says "as shown in the diagram", so it assumes θ is acute. It probably would have been clearer if it explicitly stated boundaries for θ. It also says "Let P(asec θ, btan θ) be a point....as shown in the diagram", which technically means P is chosen as a specific point (i.e. θ is a certain constant value), not a variable point.

 

[kooltrainer]

HI.. as u my already be aware.. i've done tht paper last year ..
the question is not incorrect =)



i think