Prove that: from Mathematics Trigonometric Functions

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 Multiple Choice QuestionsShort Answer Type

561.

Prove the following:

tan space left parenthesis 2 straight pi plus straight x right parenthesis space equals space tanx

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562.

Prove that tan 2 straight x space equals space fraction numerator 2 tanx over denominator 1 minus tan squared straight x end fraction.

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563.

Prove that:

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#6 {main}</pre>

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564.

Prove that:

cos 3 straight x space equals space 4 cos cubed straight x minus 3 cosx




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565.

Prove that:

space space tan 3 straight x space equals space fraction numerator 3 tanx minus tan 3 straight x over denominator 1 minus 3 space tan squared straight x end fraction




100 Views

566.

Prove that sin space 2 straight x space equals space 2 space sinx space cosx space equals space fraction numerator 2 space tanx over denominator 1 plus tan squared straight x end fraction.

102 Views

 Multiple Choice QuestionsLong Answer Type

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567.

Prove that:

cos 2 straight x space equals space cos squared straight x minus sin squared straight x space equals space 1 minus 2 sin squared straight x space equals space 2 cos squared straight x minus 1 space equals space fraction numerator 1 minus tan squared straight x over denominator 1 plus tan squared straight x end fraction.


We know that

              space space space space cos left parenthesis straight alpha plus straight beta right parenthesis space equals space cosα space cosβ space minus space sinα space sinβ

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#6 {main}</pre> by x, we get

                         cos(x + x) = cosx. cosx - sinx. sinx

∴                           cos 2x = cos squared straight x minus sin squared straight x                                                           ...(A)

Also, we know that  cos squared straight x plus sin squared straight x equals 1
∴                             cos squared straight x space equals space 1 minus sin squared straight x                                                               ...(i)
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#6 {main}</pre>                                                              ...(ii)

Putting (i) in (A), we get
                                 cos space 2 straight x space equals space 1 minus sin squared straight x minus sin squared straight x

                                 cos space 2 straight x space equals space 1 minus 2 sin squared straight x                                                           ...(B)

Putting (ii) in (A), we get
                                 cos space 2 straight x space equals space cos squared straight x minus left parenthesis 1 minus cos squared straight x right parenthesis

                                  cos space 2 straight x space equals space 2 cos squared straight x minus 1                                                         ...(C)

Now,             cos space 2 straight x space equals space fraction numerator cos squared straight x minus sin squared straight x over denominator 1 end fraction equals fraction numerator cos squared straight x minus sin squared straight x over denominator cos squared straight x plus sin squared straight x end fraction equals fraction numerator begin display style fraction numerator cos squared straight x over denominator cos squared straight x end fraction end style minus begin display style fraction numerator sin squared straight x over denominator cos squared straight x end fraction end style over denominator begin display style fraction numerator cos squared straight x over denominator cos squared straight x end fraction end style plus begin display style fraction numerator sin squared straight x over denominator cos squared straight x end fraction end style end fraction          
∴              space space space space space cos space 2 straight x space equals space fraction numerator 1 minus tan squared straight x over denominator 1 plus tan squared straight x end fraction.                                                                    ....(D)

From (A), (B), (C) and (D), we have
             
                       cos space 2 straight x space equals space cos squared straight x minus sin squared straight x equals 1 minus 2 sin squared straight x equals 2 cos squared straight x minus 1 equals fraction numerator 1 minus tan squared straight x over denominator 1 plus tan squared straight x end fraction.
          

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 Multiple Choice QuestionsShort Answer Type

568.

Prove that: cosA. space cos open parentheses straight pi over 3 minus straight A close parentheses. space cos open parentheses straight pi over 3 plus straight A close parentheses space equals space 1 fourth cos 3 straight A.

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569.

Prove that: <pre>uncaught exception: <b>mkdir(): Permission denied (errno: 2) in /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/util/sys/Store.class.php at line #56mkdir(): Permission denied</b><br /><br />in file: /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/util/sys/Store.class.php line 56<br />#0 [internal function]: _hx_error_handler(2, 'mkdir(): Permis...', '/home/config_ad...', 56, Array)
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#6 {main}</pre>

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570.

Prove that:  

space space cos open parentheses straight x over 2 close parentheses space equals space plus-or-minus square root of fraction numerator 1 plus cosx over denominator 2 end fraction end root

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