document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=846190>Question 846190</A>: <I><SPAN STYLE=\"word-break: break-all;\"> a and b are positive acute angles. if sin a= 3/5 and cos b= 12/13, find the value of cos(a-b) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #509651 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=509651\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> a and b are positive acute angles. if sin a= 3/5 and cos b= 12/13, find the value of cos(a-b)<BR>\n" );
document.write( "***<BR>\n" );
document.write( "Identity: cos(a-b)=cos a cos b+sin a sin b<BR>\n" );
document.write( "..<BR>\n" );
document.write( "sin a=3/5<BR>\n" );
document.write( "cos a=4/5<BR>\n" );
document.write( "cos b=12/13<BR>\n" );
document.write( "sin b=5/13<BR>\n" );
document.write( "..<BR>\n" );
document.write( "cos(a-b)=4/5*12/13+3/5*5/13=48/65+15/65=63/65<BR>\n" );
document.write( "..<BR>\n" );
document.write( "calculator check:<BR>\n" );
document.write( "sin a=3/5<BR>\n" );
document.write( "a=36.87&#730;<BR>\n" );
document.write( "..<BR>\n" );
document.write( "cos b&#8776;12/13<BR>\n" );
document.write( "b&#8776;22.62&#730;<BR>\n" );
document.write( "..<BR>\n" );
document.write( "a-b&#8776;14.25&#730;<BR>\n" );
document.write( "..<BR>\n" );
document.write( "cos(a-b)&#8776;cos(14.25)&#8776;0.9692<BR>\n" );
document.write( "exact ans:<BR>\n" );
document.write( "cos(a-b)=63/65&#8776;0.9692 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );