IIT JEE , AIEEE Forum - Mathematics , Trignometry

anchitsaini

this is a qn based on boundary conditions(or something like that)--

max value of L.H.S= root(20^2 + 21^2)
=29

min value of R.H.S=
is at
y= -b /2a
=18 / 2*81
=1/9

at this value of y,
value of quadratic=1-2+30=29

thus we'll get soln only when L.H.S=R.H.S=29
for L.H.S to be 29

20 sin x - 21 cos x = 29
20/29 sin x - 21/29 cos x = 1
sin @=20/29
cos @=21/29

cos(@+x)=-1=cos(pi)
@+x=2npi (+ -) pi
x= [2npi (+ -) pi ]-@

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