ATAR Notes: Forum

VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Specialist Mathematics => Topic started by: Martoman on October 11, 2010, 08:33:02 pm

Title: itute 2010
Post by: Martoman on October 11, 2010, 08:33:02 pm

i refuse to believe question 9. It says that the diagonal can be described by PR is 1/2(OP PLUS OR). No. I think with vectors its 1/2(OR MINUS OP). Anyone feel the same way? or have a missed something fundamental?

Title: Re: itute 2010
Post by: googoo on October 11, 2010, 09:17:56 pm

could you elaborate

Title: Re: itute 2010
Post by: Martoman on October 11, 2010, 10:17:22 pm

Err say any rectangle in space. Its sides are ABCD. AC = AD. Now AC = OC-OA yes? and so AX which is the midpoint is 1/2(OC-OA) and NOT 1/2(OC+OA)???

Title: Re: itute 2010
Post by: luken93 on October 11, 2010, 10:19:12 pm

Quote from: Martoman on October 11, 2010, 08:33:02 pm

i refuse to believe question 9. It says that the diagonal can be described by PR is 1/2(OP PLUS OR). No. I think with vectors its 1/2(OR MINUS OP). Anyone feel the same way? or have a missed something fundamental?

whatever martoman says goes :)

Title: Re: itute 2010
Post by: Martoman on October 11, 2010, 10:22:40 pm

LOL...............

I must be missing something or itute have just failed on a 5 mark question in their newest exam.. you'd think they'd check these things..

Title: Re: itute 2010
Post by: luken93 on October 11, 2010, 10:24:03 pm

Quote from: Martoman on October 11, 2010, 10:22:40 pm

LOL...............

I must be missing something or itute have just failed on a 5 mark question in their newest exam.. you'd think they'd check these things..

Thats your job haha

Title: Re: itute 2010
Post by: itolduso on October 11, 2010, 10:52:18 pm

please explain

Title: Re: itute 2010
Post by: roberto on October 12, 2010, 01:21:53 am

Quote from: itolduso on October 11, 2010, 10:52:18 pm

please explain

ditto. i don't get it?

Title: Re: itute 2010
Post by: googoo on October 12, 2010, 12:12:44 pm

Quote from: Martoman on October 11, 2010, 08:33:02 pm

i refuse to believe question 9. It says that the diagonal can be described by PR is 1/2(OP PLUS OR). No. I think with vectors its 1/2(OR MINUS OP). Anyone feel the same way? or have a missed something fundamental?

What is the problem?

Title: Re: itute 2010
Post by: kamil9876 on October 12, 2010, 01:05:09 pm

Quote from: Martoman on October 11, 2010, 10:17:22 pm

Err say any rectangle in space. Its sides are ABCD. AC = AD. Now AC = OC-OA yes? and so AX which is the midpoint is 1/2(OC-OA) and NOT 1/2(OC+OA)???

You are confusing position vectors with other kinds of 'displacement' vectors. 0.5(OC+OA) gives the position vector of the midpoint of C and A, ie OX.

You got the expression for AX right but to get OX you need to notice: OX=OA+0.5(OC-OA) since you are travelling starting from A to get to X. 0.5(OC-OA) is the displacement going from A to X.