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[Post New]22 Feb 2008 00:00:00 IST
    Subject: Re:Trignometry
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chetan_kp (278)

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Olaaa!! Perrrfect answer. 44  [73 rates]
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Q.1)given 20sin2@ + 21cos@ - 24=0 ,7pie/4<@<2pie,find cot@/2
 20 - 20cos2@ + 21cos@ - 24 = 0
solving u get cos@ = 1/4 or 4/5
but 7pie/4<@<2pie      ie cos@ < 1/ 2 or cos2@ > 0.5
clearly from the two options cos@ = 4/5
cos@ = 1 - 2sin2(@/2)
4/5 = 1 - 2sin2(@/2)
solving u get sin2 (@/2) = 1/10   or cosec2(@/2) = 10
but 1+ cot2(@/2)  = cosec2(@/2)
solving u get  cot(@/2) = -3

               
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