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#1 2007-08-06 13:25:16

tony123
Member
Registered: 2007-08-03
Posts: 228

a triangle

Prove the following: if, in a triangle ABC,  BA =CB
O in atriangle
< BAO = < OAC = 20°,
< ACO = 10°,
and < OCB = 30°,
then< OBC = 80°.

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#2 2007-08-06 22:44:59

JaneFairfax
Member
Registered: 2007-02-23
Posts: 6,868

Re: a triangle

This was trickier than I thought.

Triangle.png

Last edited by JaneFairfax (2007-08-06 22:48:14)

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#3 2007-08-06 23:02:37

George,Y
Member
Registered: 2006-03-12
Posts: 1,379

Re: a triangle

What? ......

That tough?


X'(y-Xβ)=0

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#4 2007-08-06 23:19:48

JaneFairfax
Member
Registered: 2007-02-23
Posts: 6,868

Re: a triangle

There may be a simpler way; if there is, then I haven’t been able to spot it. (For example, it turns out that OA = OB. Maybe there is a straightforward way to deduce this – but I’m totally blind at the moment. Blind.gif)

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#5 2007-08-13 11:39:22

Krizalid
Member
Registered: 2007-03-09
Posts: 51

Re: a triangle

I know where you got this problem ^^

It's really nice, of course with a synthetic solution.

Not hard to find.

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