Principle Of Mathematical Induction

Question
CBSEENMA11014285

Prove the following:

(a) sin space left parenthesis straight x plus straight y right parenthesis space equals space sinx space cosy space plus space cosx space siny
(b) <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)
#1 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/util/sys/Store.class.php(56): mkdir('/home/config_ad...', 493)
#2 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/plugin/impl/FolderTreeStorageAndCache.class.php(110): com_wiris_util_sys_Store->mkdirs()
#3 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/plugin/impl/RenderImpl.class.php(231): com_wiris_plugin_impl_FolderTreeStorageAndCache->codeDigest('mml=<math xmlns...')
#4 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/plugin/impl/TextServiceImpl.class.php(59): com_wiris_plugin_impl_RenderImpl->computeDigest(NULL, Array)
#5 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/service.php(19): com_wiris_plugin_impl_TextServiceImpl->service('mathml2accessib...', Array)
#6 {main}</pre>

Solution

We know that:
       cos left parenthesis straight x plus straight y right parenthesis space equals space cosx space cosy minus sinx space siny                                               ...(i)
       cos left parenthesis straight x minus straight y right parenthesis space equals space cosx space cosy space plus space sinx space siny                                               ...(ii)
                cos open parentheses straight pi over 2 minus straight x close parentheses space equals space sinx                                                             ....(iii)
               sin open parentheses straight pi over 2 minus straight x close parentheses space equals space cosx                                                               ...(iv)
(a) Replacing x by x + y, in (iii), we get
            <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)
#1 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/util/sys/Store.class.php(56): mkdir('/home/config_ad...', 493)
#2 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/plugin/impl/FolderTreeStorageAndCache.class.php(110): com_wiris_util_sys_Store->mkdirs()
#3 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/plugin/impl/RenderImpl.class.php(231): com_wiris_plugin_impl_FolderTreeStorageAndCache->codeDigest('mml=<math xmlns...')
#4 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/plugin/impl/TextServiceImpl.class.php(59): com_wiris_plugin_impl_RenderImpl->computeDigest(NULL, Array)
#5 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/service.php(19): com_wiris_plugin_impl_TextServiceImpl->service('mathml2accessib...', Array)
#6 {main}</pre>                                                  ...(v)
Also,  cos open parentheses straight pi over 2 minus left parenthesis straight x plus straight y right parenthesis close parentheses equals cos open square brackets open parentheses straight pi over 2 minus straight x close parentheses minus straight y close square brackets equals cos open parentheses straight pi over 2 minus straight x close parentheses cosy plus sin open parentheses straight pi over 2 minus straight x close parentheses siny
                                                                                                      [By using (ii)]
                                 = sinx cosy + cosx siny                   [By using (iii) and (iv)]
Hence,             sin(x+y) = sinx cosy + cosx siny
(b) Replacing y by - y in (v), we get
         sin(x-y) = sinx cos(-y) + cosx sin(-y)
                      = sinx cosy - cosx siny         [∵ cos(-y) = cosy, sin(-y) = - siny]
Hence,   sin(x-y) = sinx cosy - cosx siny
    
        
       

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