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Trignometry

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4 Jun 2007 22:09:07 IST

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trignometry......pls help

None

if tan (pi cos

) = cot (pi sin

) then......

cos (

- pi/4) is equal to.......

a) plus or minus 1/( 2root 2)

b) plus or minus 1/root 2

c) plus or minus root 2

d) plus or minus 2 root 2

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Comments (10)

Himanshu

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Joined: 19 Feb 2007

Posts: 3834

4 Jun 2007 22:21:56 IST

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tan (pi cos#) = cot (pi sin#)

sin (pi cos#) / cos (pi cos#) = cos (pi sin#) / sin (pi sin#)

cross multiply

sin (pi cos#).sin(pi sin#) = cos(pi cos#) . cos(pi sin#)

to make it easy , take pi cos# = A , pi sin# = B

sinA.sinB = cosA.cosB

cosA.cosB - sinA.sinB = 0

cos (A+B) = 0

A+B = pi/2

picos# + pisin# = pi/2

i have come upto here........solving jst tell me m i rite???????

sneha kulkarni

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Posts: 297

4 Jun 2007 22:24:06 IST

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even i got till the fourth step.......but further m clueless.....

sneha kulkarni

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Posts: 297

4 Jun 2007 22:27:12 IST

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hey wait a min.......i think u r rite.....
so i got the clue...
it will b
pi cos # = pi/2 - pi sin #
cos # + sin # = plus or minus 1/2
root 2 cos ( # - pi/4 ) = 1/2
cos (# -pi/4 ) = 1/ 2 root 2.....
is it rite????

Ninja Storm

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4 Jun 2007 22:29:50 IST

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You all shut up I am the Rated R superstar.You may be a spear away from being knocked out ?????//

anshul sharma

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4 Jun 2007 22:37:35 IST

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is this the answer given?????????????

1/2root 2?????????????

@ninjastorm will u shut up................fr ur spear's sake plz don't do these carppy things here or u have to pay

anshul sharma

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Posts: 754

4 Jun 2007 22:38:42 IST

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oh sry

yes i think above ans is correct

sneha kulkarni

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4 Jun 2007 22:39:42 IST

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i don know anshul.....itz not given...
but itz the same ans i got.......

sneha kulkarni

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4 Jun 2007 22:43:51 IST

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well.....thanx himanshu and anshul...!!

ravi tej

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4 Jun 2007 22:46:36 IST

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its too much yar

u can have a far better sol. for that

tanx=coty implies that x+y is an odd multiple of pi/2

hence (sin+cos)=(2n+1)/2

since the max value of sin+cos is root2

sin+cos=1/2 or -1/2

dividing both sides with root2 , cos(/4-) is 1/22

Akansha

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Joined: 16 Apr 2007

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4 Jun 2007 22:59:15 IST

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sin(

cos

)/cos(

cos

)=cos(

sin

)/sin(

sin

)

=>cos(

cos

)cos(

sin

)-sin(

sin

)sin(

cos

)=0

=>cos(

(sin

+cos

))=0=cos+/-

=>sin

+cos

=1/2

2(1/

2cos

+1/

2sin

2cos(

/4-

)= + -1/2

=>cos(

/4-

)= +1/2

2 or-1/2

a) is correct

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