geometry wonderrful - 1

IN A RIGHT TRIANGLE ACB, RIGHT ANGLED AT C ANGLE BISECTORS OF A AND B MEET BC AND AC AT P AND Q RESPECTIIVELY. M AND N ARE FEET OF PERPENDICULARS FROM P AND Q ON AB. FIND ANGLE MCN.

14 Answers

36
rahul ·

no one giving it a try.....

49
Subhomoy Bakshi ·

Answer= A+B2 ??

36
rahul ·

nopes.....

49
Subhomoy Bakshi ·

A+B2 means 45° [3]

36
rahul ·

i mean yup....
i didn't notiice that....
did u do it by plane geometry...?

49
Subhomoy Bakshi ·

My method:

A+B=90°

ΔACP ≡ ΔAPM

Thus, CP=PM

In cyclic quad. ACPM,
<CPM = 180°-A

thus in isoceles ΔBPM,
<PMC=<PCM=A2

O is the incentre..
thus,
OC is the angle bisector too..

thus, <AC0=<PCO=45°
so, <MCO= 90°-A2=B2

Similarly, it can be proved that, <NCO=A2

Thus, <MCN=A+B2=45°

36
rahul ·

my goodness.... woonderful
but there was no need of joining CO

49
Subhomoy Bakshi ·

hmmm.. Why so? I used it in my proof!

Did I go by longer way when there was a possible shorter route anywhere?
If yes please pointout..!

36
rahul ·

yup it is....
but trully typical to post it from
the cell phone...
wt let me prepare a rgh sketch
just try to understand it...
coz my drawing is worst.... :o

49
Subhomoy Bakshi ·

I can never access targetiit from cell....:(
It just shows the first 2 posts!

How do u manage to POST from cell?? :O

36
rahul ·

i too had the samee problem
but in the setinngs option enable the mobile view.... in opera mini

failed to uupload the img forrmat is png

last option camera wtt...

49
Subhomoy Bakshi ·

a step shortener will be:

<MCB=A/2

similarly, <NCA=B/2

Thus reqd angle= 90°-(A+B)/2 = 45°

36
rahul ·

in ur figure
it is easy to observe that BQ inttersects CN at right angles.
which leads to
LPAC + LACN = 45°
OR, LCNO = 45°
OR, LMCN = 45°
now which was better

49
Subhomoy Bakshi ·

nice nice! [4][1]

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