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Geometry Level 5

A rectangular hyperbola is cut by a circle of radius 2 2 units in 4 4 distinct points A , B , C A,B,C and D D .Let O O be the center of the rectangular hyperbola.

Find the maximum value of O A + O B + O C + O D OA+OB+OC+OD .


The answer is 8.00.

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2 solutions

the MOTHER of over-rated questions :P Simply take a circle with centre as origin and the rectangular hyperbola with the same centre.So the ans would be 8 .Although I guess its gonna be done in formal way as using Cauchys inequality yields the sum is 8 .So the maximum is 8.

Harsh Shrivastava
Feb 27, 2017

Hint:Cauchy Schwartz might be helpful.

You know what I did.Simply take a circle with centre as origin and the rectangular hyperbola with the same centre.So the ans would be 2 + 2 + 2 + 2 = 8 2+2+2+2=8 .Although I guess its gonna be done in formal way as O A 2 + O B 2 + O C 2 + O D 2 = 4 R 2 OA^2+OB^2+OC^2+OD^2=4R^2 .Then using Cauchys inequality yields the sum is O A + O B + O C + O D < = 8 OA+OB+OC+OD<=8 .So the maximum is 8.

Spandan Senapati - 4 years, 3 months ago

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Yup the last one is the thing I did.And yes your first statement is the equality condition.

Harsh Shrivastava - 4 years, 3 months ago

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Good.keep posting more maths problems

Spandan Senapati - 4 years, 3 months ago

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@Spandan Senapati Yup if I come across any good one I will post.You aso post some jee lvl physics probs!

Harsh Shrivastava - 4 years, 3 months ago

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@Harsh Shrivastava Ya sure....I will post some good jee questions.....And I haven't posted a maths q till now!!

Spandan Senapati - 4 years, 3 months ago

@Harsh Shrivastava Hey can you just help me-I encountered (lni) today.Is its value ( ( 2 n + 1 / 2 ) π (2n+1/2)π or simply π / 2 π/2 ).confused....

Spandan Senapati - 4 years, 3 months ago

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@Spandan Senapati What is ini?Intigration?

I'll try my best.Post it!

Harsh Shrivastava - 4 years, 3 months ago

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@Harsh Shrivastava No its rather logi(base e) or natural logarithm of i.is the square root of -1.(just to make clear)

Spandan Senapati - 4 years, 3 months ago

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@Spandan Senapati If you talk about principle value then it is just pi/2.Else since ln is a multivalued function,we have that general solution.

Harsh Shrivastava - 4 years, 3 months ago

Bro your marks in inpho?selected?

Harsh Shrivastava - 4 years, 3 months ago

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No I did nt get selected.Will try next yr.I guess 3 from 11 and 34 from 12th have been selected.I could not complete my paper and had messed up the graphs...which carried more than 25 marks.

Spandan Senapati - 4 years, 3 months ago

Not even sarthak..We were the only 2 from 11th from odisha and only 7 appeared for inpho😀😀

Spandan Senapati - 4 years, 3 months ago

Bro comment on the kvpy interview forum.This is meant for discussions to your problem I guess.cheers.☺☺

Spandan Senapati - 4 years, 3 months ago

Yep i did the same!. I Will be posting jee level problems after mains most probably when i will revise for jee advanced

Prakhar Bindal - 4 years, 3 months ago

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OK.....BTW you got selected in chem??

Spandan Senapati - 4 years, 3 months ago

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@Spandan Senapati Well not actually . Paper had loads of extra jee stuff (biochemistry and biomolecules) which i didn't prepared due to lack of time and of course i did not wanted to deviate from jee syllabus

Prakhar Bindal - 4 years, 3 months ago

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@Prakhar Bindal No issues.Jee is more imp.Even I didn't get selected in inpho.although I worked hard this time.But as of now since my jee physics is almost over I will work hard this time again for inpho.

Spandan Senapati - 4 years, 3 months ago

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@Spandan Senapati Well cool . i am sure you will get through next year. Best of luck!.

Even i had minimum expectations from myself hence i didn't found it shocking or so

Prakhar Bindal - 4 years, 3 months ago

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@Prakhar Bindal Best of luck..go on you have a lot many xms awaiting for you......I am sure you will give your best.......Best of luck☺☺(fav smiley)

Spandan Senapati - 4 years, 3 months ago

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@Spandan Senapati Yep thanx a lot

Prakhar Bindal - 4 years, 3 months ago

@Prakhar Bindal Ya olympiads courses generally diverge from jee syllabi.

Spandan Senapati - 4 years, 3 months ago

Yeah.....did the same way!!!!

A Former Brilliant Member - 4 years, 3 months ago

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