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Trignometry

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13 Jan 2008 22:23:49 IST

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512

find angle

Engineering Entrance , JEE Main , JEE Advanced , Mathematics , Trigonometry

1. sin^-1sin 10 2 .cos^-1cos 10

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anand bhanushali

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Joined: 2 Jan 2008

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13 Jan 2008 22:33:08 IST

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1 10
2 10

aNdRoMeDa

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Joined: 10 Sep 2007

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13 Jan 2008 22:35:04 IST

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nupz

ur ansewr is wrng i guess

sininverse is outside

so d value inside shud b betwn or in d range of sin inverse n cos inverse

i guess d answer id 10-3pi

do correct if i m wrng

Learner .

Blazing goIITian

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13 Jan 2008 22:46:52 IST

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Even I thought it would be 10 in both cases...

Deedee,could you please tell when it will be so(i mean 10)?

Rohit Gupta

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13 Jan 2008 22:47:14 IST

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sin 10 = sin (3*pi + (10 - 3*pi)) = - sin (10 - 3*pi) = sin (3*pi - 10)

=> sin-1(sin 10) = sin-1(sin (3*pi - 10)) = 3*pi - 10 = - (10 - 3*pi) ANS
lies in [-pi/2, +pi/2] i.e. range of sine inverse

cos 10 = cos (4*pi - (4*pi - 10)) = cos (4*pi - 10)

=> cos-1(cos 10) = cos-1(cos (4*pi - 10)) = 4*pi - 10 ANS
ans lies in [0, pi] i.e. range of cosine inverse

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