document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=78790>Question 78790</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Can someone please help, I have a test tommorow and have no clue what to do on this problem.<BR>\n" );
document.write( "given sinx=1/4 and 0<x<pi/2, find the exact value of sin2x </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #56544 by </B><A HREF=/tutors/aboutme.mpl?userid=mathdoc314><B>mathdoc314(58)</B></A><img src=\"/images/stars/stars-08.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mathdoc314><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=56544\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> This can be solved with a double-angle formula\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+sin+2x+=+2+sin+x+cos+x+ ALIGN=MIDDLE  ALT=\"+sin+2x+=+2+sin+x+cos+x+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+cos+2x+=+cos%5E2+%28x%29+-+sin%5E2+%28x%29+ ALIGN=MIDDLE  ALT=\"+cos+2x+=+cos%5E2+%28x%29+-+sin%5E2+%28x%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" > <BR>\n" );
document.write( "(I remember it better if I see them both at once)\r<BR>\n" );
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document.write( "That x is in the first quadrant is useful to know because there you know that the cosine is positive.  Therefore, since <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+sin%5E2+%28x%29+%2B+cos%5E2+%28x%29+=+1+ ALIGN=MIDDLE  ALT=\"+sin%5E2+%28x%29+%2B+cos%5E2+%28x%29+=+1+\"   DISABLED_style= \"max-width:90%; height:auto;\" >, you can solve and find <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+cos+x+=+sqrt%281+-+%281%2F4%29%5E2%29+ ALIGN=MIDDLE  ALT=\"+cos+x+=+sqrt%281+-+%281%2F4%29%5E2%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+sqrt%2815%2F16%29+ ALIGN=MIDDLE  ALT=\"+sqrt%2815%2F16%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+sqrt%2815%29%2F4+ ALIGN=MIDDLE  ALT=\"+sqrt%2815%29%2F4+\"   DISABLED_style= \"max-width:90%; height:auto;\" >.\r<BR>\n" );
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document.write( "The double angle formula for <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sin%282x%29 ALIGN=MIDDLE  ALT=\"sin%282x%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > tells me <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+sin%282x%29+=+2+%2A+%281%2F4%29+%2A+%28sqrt%2815%29%2F4%29+=+%0D%0A%28sqrt%2815%29%29%2F8+ ALIGN=MIDDLE  ALT=\"+sin%282x%29+=+2+%2A+%281%2F4%29+%2A+%28sqrt%2815%29%2F4%29+=+%0D%0A%28sqrt%2815%29%29%2F8+\"   DISABLED_style= \"max-width:90%; height:auto;\" > exactly. </SPAN>\n" );
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