document.write( "Question 1203962: If $\"+cos%28beta%29+=+-3+%2F+5+\"$ then, without a calculator, find $\"cos%28pi+%2F+2+-+beta%29+\"$ . Write your answer as a fraction. \n" ); document.write( "

Algebra.Com's Answer #839910 by MathLover1(20850) $\"\"$ $\"About$

You can put this solution on YOUR website!

\n" ); document.write( "If $\"+cos%28beta%29+=+-3+%2F+5+\"$ then, without a calculator, find $\"cos%28pi+%2F+2+-+beta%29+\"$ . Write your answer as a fraction.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "use identity: \r
\n" ); document.write( "\n" ); document.write( " $\"cos%28pi%2F2+-+beta%29+=sin%28beta%29\"$ \r
\n" ); document.write( "\n" ); document.write( "and \r
\n" ); document.write( "\n" ); document.write( " $\"sin%28beta%29=sqrt%281-cos%5E2%28beta%29%29\"$ \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "given that\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " $\"cos%28beta%29+=+-3+%2F+5+\"$ , then\r
\n" ); document.write( "\n" ); document.write( " $\"cos%5E2%28beta%29+=%28+-3+%2F+5%29%5E2+\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"cos%5E2%28beta%29+=9+%2F25+\"$ \r
\n" ); document.write( "\n" ); document.write( "substitute in $\"sin%28beta%29=sqrt%281-cos%5E2%28beta%29%29\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"sin%28beta%29=sqrt%281-9+%2F25+%29\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"sin%28beta%29=sqrt%2816%2F25+%29\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"sin%28beta%29=4%2F5+\"$ or $\"sin%28beta%29=+-4%2F5+\"$ \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "so, $\"cos%28pi+%2F+2+-+beta%29+=4%2F5+\"$ or $\"cos%28pi+%2F+2+-+beta%29+=+-4%2F5+\"$ \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

\n" );