external section formula

For students of class 11-12 (age 16+)
kh ibrahim
Posts:17
Joined:Mon May 09, 2016 11:18 am
external section formula

Unread post by kh ibrahim » Fri Oct 07, 2016 2:37 am

I'm facing trouble in the external section formula in vectors.here it is
Attachments
rps20161007_023032.jpg
external section formula.I don't know which is correct.need the solution
rps20161007_023032.jpg (125.21KiB)Viewed 9741 times

kh ibrahim
Posts:17
Joined:Mon May 09, 2016 11:18 am

Re: external section formula

Unread post by kh ibrahim » Fri Oct 07, 2016 2:40 am

the second part of that external section formula.
Attachments
rps20161007_022523.jpg
external section formula.the second part is here.picture
rps20161007_022523.jpg (29.54KiB)Viewed 9740 times

kh ibrahim
Posts:17
Joined:Mon May 09, 2016 11:18 am

Re: external section formula

Unread post by kh ibrahim » Fri Oct 07, 2016 2:41 am

I don't know which is correct or why that would be correct.

User avatar
Phlembac Adib Hasan
Posts:1016
Joined:Tue Nov 22, 2011 7:49 pm
Location:127.0.0.1
Contact:

Re: external section formula

Unread post by Phlembac Adib Hasan » Fri Oct 07, 2016 8:51 am

Both of the formulae are correct. $C$ is not on the same end of $\vec{AB}$ in both proofs. That's why the formula changes.

Actually, there is no special formula called external section formula. It's just the internal section formula with one of the ratios being negative.
Welcome to BdMO Online Forum. Check out Forum Guides & Rules

kh ibrahim
Posts:17
Joined:Mon May 09, 2016 11:18 am

Re: external section formula

Unread post by kh ibrahim » Fri Oct 07, 2016 1:12 pm

How can a ratio be negative?Is it because of different direction?

User avatar
Phlembac Adib Hasan
Posts:1016
Joined:Tue Nov 22, 2011 7:49 pm
Location:127.0.0.1
Contact:

Re: external section formula

Unread post by Phlembac Adib Hasan » Sun Oct 09, 2016 10:02 am

Yeah. Vector lengths are direction sensitive.
Welcome to BdMO Online Forum. Check out Forum Guides & Rules

kh ibrahim
Posts:17
Joined:Mon May 09, 2016 11:18 am

Re: external section formula

Unread post by kh ibrahim » Sun Oct 09, 2016 2:17 pm

Lets talk out of vectors.Supposing if a point C divides a line segment AB externally what would it mean?Will it mean C is closer to A or B?Why would it mean so?

Post Reply