ATAR Notes: Forum

VCE Stuff => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematics => Topic started by: annie on November 02, 2008, 06:48:50 pm

Title: vector proofs
Post by: annie on November 02, 2008, 06:48:50 pm

Hi guys i was just doing some trial exams for spesh paper 1, and i came across a vector proof question on my 9th paper  :o

it was something like prove that OACB is a Rhombus
given that AB is perpendicular to OC

and it stumped me because i don't know the prequisite conditions in order to prove that something is a shape

can someone tell me a general list of what 'shapes' i should know and their prequisites??

eg. rhombus - must have 4 equal sides etc??

thanks alot

Title: Re: vector proofs
Post by: Mao on November 02, 2008, 07:30:34 pm

parallelogram - one pair of opposite sides are parallel and same magnitude
rectangle - parallelogram + one right angle
rhombus - four equal sides
square - rhombus + one right angle

[the triangles are pretty self explanatory]

Title: Re: vector proofs
Post by: trinon on November 02, 2008, 08:12:32 pm

Refer to image attached.

Isn't it that if you can prove that OB.AC = 0, it's a rhombus?

Title: Re: vector proofs
Post by: ice_blockie on November 02, 2008, 08:21:39 pm

Quote from: trinon on November 02, 2008, 08:12:32 pm

Refer to image attached.

Isn't it that if you can prove that OB.AC = 0, it's a rhombus?

In short no. Draw a kite and then you will see why...