document.write( "Question 1131350: I'm working on trig identities. some are simple, some not.
\n" ); document.write( "I see comments about working on one side only. why is that?
\n" ); document.write( "Does it make a difference?
\n" ); document.write( "if so, can you show a problem wehre is does make a difference? \n" ); document.write( "
Algebra.Com's Answer #748014 by Edwin McCravy(20059)\"\" \"About 
You can put this solution on YOUR website!
The reason is that you cannot assume from the start that what is \r\n" );
document.write( "given is really an identity, since that is what you are to prove.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "Here is an example.  We start with a NON-identity:\r\n" );
document.write( "\r\n" );
document.write( "sin(x) + cos(x) = -sin(x) - cos(x)    \r\n" );
document.write( "\r\n" );
document.write( "Square both sides:\r\n" );
document.write( "\r\n" );
document.write( "sinē(x) + 2sin(x)cos(x) + cosē(x) = sinē(x) + 2sin(x)cos(x) + cosē(x)\r\n" );
document.write( "\r\n" );
document.write( "Both sides are exactly equal.\r\n" );
document.write( "\r\n" );
document.write( "So if you were allowed to square both sides, you would be able to\r\n" );
document.write( "prove that some NON-identities were identities!!!\r\n" );
document.write( "\r\n" );
document.write( "Edwin
\n" ); document.write( "
\n" );