Pure geometry topics application for JEE

Geometry Level 4

x 2 sin ( 2 ) sin ( 3 ) + y 2 cos ( 2 ) cos ( 3 ) = 1 \frac{x^2}{\sin(\sqrt{2})-\sin(\sqrt{3})}+\frac{y^2}{\cos(\sqrt{2})-\cos(\sqrt{3})}=1

The curve represented by the equation above is?

a hyperbola with focii on y y -axis an ellipse with focii on x x -axis a hyperbola with focii on x x -axis an ellipse with focii on y y -axis None of this choices

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1 solution

Tanishq Varshney
Mar 12, 2015

surely not a level 5 problem, can be solved mentally with in 15 sec.

the graph of s i n x sinx between [ 0 , π ] [0,\pi] is symmetrical about x = π 2 x=\frac{\pi}{2}

and π 2 = 1.507 \frac{\pi}{2}=1.507

also 2 = 1.414 \sqrt{2} =1.414 and 3 = 1.732 \sqrt{3}=1.732

we see that 1.414 is closer to 1.507 than 1.732, so s i n ( 2 ) > s i n ( 3 sin(\sqrt{2})>sin(\sqrt{3}

similarly from graph c o s ( 3 ) = n e g a t i v e cos(\sqrt{3})=negative v a l u e value

the denominator of y 2 y^2 is greater as the are added up ,so the answer follows an ellipse with focii on y axis

do upvote

I did it the same way. Definitely overrated . :)

Keshav Tiwari - 6 years, 1 month ago

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