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cute_ria (36)

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Q.Let p{sin,cos}where 0  2 be a pt  nd let oab be a triangle with vertices{0,0},{ 3/2 , 0} nd {0,3/2}.find  if p lies inside the OAB.
 
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sachin_gupta1991 (69)

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I think the answer is  lies between 30 degrees and 60 degrees.
I am giving details in a few minutes.
 
 
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sachin_gupta1991 (69)

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As one cordinate is (sin60,0),and p lies withinn the triangle <60.
As another coordinate is (0,cos30),and p lies withinn the triangle
theta>30.
{Draw the figure after drawing x and y-axis, u will get the logic.}
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spideyunlimited (3473)

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locus of point p will be x2 + y2 = 1  . a circle    ( as (sin2 + cos2) = 1  )
also we can find the equation of the line which forms the triangle with the x and y axes...
y - (3/2)  = ( (3/2) - 0  ) / ( 0 - (3/2) )       X      (x - 0)
 
y = -x + (3/2)
 
 
find points of intersection....
 
as y is cos    and x is sin  acc. to question therefore
cos   = - sin  + (3/2)
solving,
cos  + sin   = (3/2)
divide both sides by 2 and use formula of sin( a + b)
 
we get sin( pi/4  +   )  =  3   /   2 
 
 = pi / 12  , 5 pi / 12     for  1st quadrant  as the triangle is there
 
thus, point p will be ON the triangle for these values of
and also for  = 0 and pi/2 as at these values sin gives x axis and y axis which r the other 2 sides of the triangle.
 
thus  E ( 0 , pi/12)  U  ( 5 pi/12 , pi /2)
 
 
 
PS. check it out by drawing also . my point will become clear to you
 
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