document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=777560>Question 777560</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Find (Cos a-b) given that Cos a= 5/13 and cos b= 3/5 and that both are between 0 and &#960;/2. Show all work please. Stumped on the identities. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #474423 by </B><A HREF=/tutors/aboutme.mpl?userid=lwsshak3><B>lwsshak3(11628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=lwsshak3><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=474423\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Find (Cos a-b) given that Cos a= 5/13 and cos b= 3/5 and that both are between 0 and &#960;/2.<BR>\n" );
document.write( "***<BR>\n" );
document.write( "cos(a-b)=cos a*cos b+sin a*sin b<BR>\n" );
document.write( "given cos a=5/13<BR>\n" );
document.write( "sin a=&#8730;(1-cos^2a)=&#8730;(1-(25/169))=&#8730;(144/169)=12/13<BR>\n" );
document.write( "given cos b=3/5<BR>\n" );
document.write( "sin b=&#8730;(1-cos^2b)=&#8730;(1-(9/25))=&#8730;(16/25)=4/5<BR>\n" );
document.write( "cos(a-b)=5/13*3/5+12/13*4/5=15/65+48/65=63/65  </SPAN>\n" );
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