Dhaka Secondary 2009/3

Problem for Secondary Group from Divisional Mathematical Olympiad will be solved here.
Forum rules
Please don't post problems (by starting a topic) in the "Secondary: Solved" forum. This forum is only for showcasing the problems for the convenience of the users. You can post the problems in the main Divisional Math Olympiad forum. Later we shall move that topic with proper formatting, and post in the resource section.
BdMO
Posts:134
Joined:Tue Jan 18, 2011 1:31 pm
Dhaka Secondary 2009/3

Unread post by BdMO » Tue Feb 01, 2011 11:49 pm

$ABC$ is a right angle triangle where $A$ is the right angle. $D$ is a point on $AC$ so
that $AB=AD$. $E$ & $F$ bisect $BD$ & $AD$ respectively. $DH \bot BC$ & $DH=\sqrt{2}$. Find the $\angle DCH$ when $EF=1$.

User avatar
Tahmid Hasan
Posts:665
Joined:Thu Dec 09, 2010 5:34 pm
Location:Khulna,Bangladesh.

Re: Dhaka Secondary 2009/3

Unread post by Tahmid Hasan » Wed Feb 02, 2011 12:02 am

15 degree,again similar triangles and trigonometry.
বড় ভালবাসি তোমায়,মা

photon
Posts:186
Joined:Sat Feb 05, 2011 3:39 pm
Location:dhaka
Contact:

Re: Dhaka Secondary 2009/3

Unread post by photon » Tue Feb 08, 2011 3:05 pm

DHC and ABC are similar.\[so \frac{CD}{BC}=\frac{CH}{AC}=\frac{DH}{AB}=\frac{1}{\sqrt{2}}\]
from this ,we need to make \[\frac{CD}{CH} or \frac{AB}{AC}\]
or anything else and may find C with trigonometric ratios.
it's my way(may be same) but how to value these factions?that makes to do 1st similarity eqtn ''ekantorkoron''
it then changes value.please,help.
Try not to become a man of success but rather to become a man of value.-Albert Einstein

Post Reply