document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=146543>Question 146543</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I am  having a problem understanding where the answer is coming from in this question. Any assistance would be appreciated.  The question is, a plane flies at a bearing due east from the airport for 120 km. It changes directon to 30 degrees and then travels and additional 50 km.  How far is the plane from the airport.  I used the Law of Cosines of c^2 = a^2 + b^2 - 2abCosC.  Which I used a = 50 and b = 120. Cos C = 30 degrees. So my final answer is 2500 + 14,400 - 2(50)(120)*.8666 = 6500. a^2 = 6500 = 80.62 km. \r<BR>\n" );
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document.write( "But the answer says I should be using a^2 = b^2 + c^2-2bc CosA. They use 120 for b and 50 for C and 120 degrees for Cosine A.  Answer is 151 km.  Please advise why I am to be using Cos 120 and not Cos30.  I am reading if it says it changes direction to 30 degrees, not just 30 degrees, that it is going north towards 30 degrees,  Perhaps this is not correct.  Thank you.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #107008 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><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/cgi-bin/show-face.mpl?user=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=107008\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> 120 degs is the angle between the 2 headings.<BR>\n" );
document.write( "\"Due East\" is a heading of 090. If you draw that, then draw a line from the end of it heading 030, you'll see that.  It's a change of direction of 60 degs, but the internal angle is 120.<BR>\n" );
document.write( "A heading of 030 is 30 degs \"to the right\" of vertical. </SPAN>\n" );
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