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Motion In A Plane

Question
CBSEENPH11018058

Show that:
open vertical bar straight A with rightwards arrow on top plus straight B with rightwards arrow on top close vertical bar less-than or slanted equal to open vertical bar straight A with rightwards arrow on top close vertical bar space plus space open vertical bar straight B with rightwards arrow on top close vertical bar greater-than or slanted equal to space open vertical bar open vertical bar straight A with rightwards arrow on top close vertical bar minus open vertical bar straight B with rightwards arrow on top close vertical bar close vertical bar

Solution

To show: 
open vertical bar straight A with rightwards arrow on top plus straight B with rightwards arrow on top close vertical bar space equals square root of straight A squared plus straight B squared plus 2 ABcosθ end root

Since <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>,
open vertical bar straight A with rightwards harpoon with barb upwards on top plus straight B with rightwards harpoon with barb upwards on top close vertical bar space less-than or slanted equal to space square root of straight A squared plus straight B squared plus 2 AB end root

space space space space space space space space space space space space space space equals space square root of left parenthesis straight A plus straight B right parenthesis squared end root

space space space space space space space space space space space space space space equals space straight A space plus space straight B

Therefore comma space

open vertical bar straight A with rightwards harpoon with barb upwards on top space plus space straight B with rightwards harpoon with barb upwards on top close vertical bar less-than or slanted equal to open vertical bar straight A with rightwards harpoon with barb upwards on top space close vertical bar space plus space open vertical bar space straight B with rightwards harpoon with barb upwards on top close vertical bar space

Now comma space open vertical bar straight A with rightwards harpoon with barb upwards on top space plus space straight B with rightwards harpoon with barb upwards on top close vertical bar space equals space square root of straight A squared plus straight B squared plus 2 ABcosθ end root

Since comma space cos space straight theta space greater-than or slanted equal to space minus space 1

therefore space open vertical bar straight A with rightwards harpoon with barb upwards on top space plus space straight B with rightwards harpoon with barb upwards on top close vertical bar greater-than or slanted equal to space square root of straight A squared plus straight B squared minus 2 AB end root space

space space space space space space space space space space space space space space space space space space space equals square root of left parenthesis straight A minus straight B right parenthesis squared end root

space space space space space space space space space space space space space space space space space space space equals open vertical bar straight A with rightwards harpoon with barb upwards on top space minus space straight B with rightwards harpoon with barb upwards on top close vertical bar

space space space space space space space space space space space space space space space space space space space space equals space open vertical bar open vertical bar straight A with rightwards harpoon with barb upwards on top close vertical bar plus open vertical bar straight B with rightwards harpoon with barb upwards on top close vertical bar close vertical bar
Hence proved.