document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=365266>Question 365266</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Evaluate cos(2sin^-1(4/5)) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #260408 by </B><A HREF=/tutors/aboutme.mpl?userid=robertb><B>robertb(5830)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=robertb><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=robertb><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=260408\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Let A = 2sin^1(4/5).  Then A/2 = sin^1(4/5), or <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sin%28A%2F2%29+=+4%2F5 ALIGN=MIDDLE  ALT=\"sin%28A%2F2%29+=+4%2F5\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  We have to find cosA.  But from the identity <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=cos+A+=+1-2sin%5E2%28A%2F2%29 ALIGN=MIDDLE  ALT=\"cos+A+=+1-2sin%5E2%28A%2F2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > we get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=cosA+=+1-2%2A%284%2F5%29%5E2+=+1-2%2A%2816%2F25%29+=+1-32%2F25+=+-7%2F25 ALIGN=MIDDLE  ALT=\"cosA+=+1-2%2A%284%2F5%29%5E2+=+1-2%2A%2816%2F25%29+=+1-32%2F25+=+-7%2F25\"   DISABLED_style= \"max-width:90%; height:auto;\" > </SPAN>\n" );
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