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prove that (tanx+cotx)^4=sec^4x csc^4x

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jule993 | Student, Grade 10 | eNotes Newbie

Posted July 3, 2012 at 9:27 PM via web

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prove that (tanx+cotx)^4=sec^4x csc^4x

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted July 4, 2012 at 5:00 AM (Answer #1)

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The identity `(tan x + cot x)^4 = sec^4 x*csc^4 x` has to be proved.

`(tan x + cot x)^4`

`tan x = sinx/cos x` and `cot x = cos x/sin x`

=> `(sin x/cos x + cos x/sin x)^4`

=> `((sin^2 x + cos^2 x)/(sin x*cos x))^4`

`sin^2x + cos^2x = 1`

=> `1/(sin x*cos x)^4`

=> `1/(sin^4 x*cos^4x)`

=> `sec^4x*cosec^4x`

This proves `(tan x + cot x)^4 = sec^4 x*csc^4 x`

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cavincavin | eNoter

Posted July 4, 2012 at 2:26 AM (Answer #2)

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(tan x + cot x)^4 = [(sinx/cosx) + (cosx/sinx)]^4

                          = [(sin^2 x + cos^2 x)/(sinx cosx)]^4

where sin^2 x + cos^2 x = 1

                          = [1/(sinx cosx)]^4

                          = (csc x . sec x)^4

                          = csc^4 x sec^4 x

                            

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chaobas | College Teacher | Valedictorian

Posted July 4, 2012 at 3:07 AM (Answer #3)

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(tan x+cotx)^4 = (sinx/cosx + cosx/sinx)^4  

                       = (sin^2 x + cos^x/(sinx cosx))^4

                       =(1/cosx. sinx)^4  [since sin^2x + cos^x= 1]

                       = (1/sinx . 1/cosx)^4

                        =(cosec x   sec x)^4

                         = cosex ^4 x . sec ^4x

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