ATAR Notes: Forum

VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Specialist Mathematics => Topic started by: 2happy on November 14, 2007, 08:47:04 pm

Title: Derive
Post by: 2happy on November 14, 2007, 08:47:04 pm

Can anyone derive the formula for a:
Hexagon
Octagon
From scratch?

i think you have to:
- use pythag
- double angle formulas
- anything else

Title: Derive
Post by: Ahmad on November 14, 2007, 09:02:29 pm

What do you mean by formula? What exactly do you want to determine?

Title: Derive
Post by: Daniel15 on November 14, 2007, 09:54:45 pm

You mean formula for area of those shapes? Or something?

Title: Derive
Post by: 2happy on November 14, 2007, 10:11:24 pm

i mean: you start with an octagon and you have to prove that the formula to find the AREA of an octagon is __________(watever it is - dont have formula nxt to me atm)

Title: Derive
Post by: Galelleo on November 15, 2007, 09:52:16 am

using what, vectors?

I find it hard to imagine theres a cartesian formula that creates a perfect octagon... :S

Title: Derive
Post by: Ahmad on November 15, 2007, 03:24:43 pm

Hint: inscribe the regular polygon in a circle, draw radius lines from the center to the vertices. Split up the shape into triangles.

Title: Derive
Post by: 2happy on November 15, 2007, 03:41:51 pm

thanks ahmad; i had the exam today: the put the octagon in a square and had circles with radius r on the vertices of the octagon (8 in total) then u had to find the area of a leftover bit: pretty hard

Title: Derive
Post by: Ahmad on November 15, 2007, 03:43:25 pm

That's the common way for an octagon, but it's not very general. ^^