Thursday 13 April 2017

linear algebra - Trouble in this circle question



Referring to this diagram (self-made):



enter image description here



Question says:





In the given figure diameter of the circle is $3$ cm. AB & MN are two diameter such that MN is perpendicular to AB. In addition CG is parallel to MN. $AE : EB = 1 : 2$ and DF is perpendicular to MN and $NL : ML = 1 : 2$, find the length of DH.




Using the ratios, I could formulate that $AE = 1 cm$ and $EB = 2cm$ and $NL = 1cm$ and $ML = 2cm$.
I could also find that $MO = A0 = BO = ON = 1.5cm$
Also, EOLH becomes a square of side 0.5 cm.



But can't figure out how to find DH.




Can someone please help.



Thanks a lot.


Answer



$OD$ is a radius of the circle as well, so has length $1.5$. $OL$ has length $0.5$. So by Pythagoras $DL$ has length $\sqrt{1.5^2 - 0.5^2} = \sqrt{2}$. And $HL$ has length $0.5$ so $DH$ has length $\sqrt 2 - 0.5$.


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