document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1100862>Question 1100862</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Rewrite the expression as the&#8203; sine, cosine, or tangent of a&#8203; double-angle. Then find the exact value of the trigonometric expression without the use of a calculator.\r<BR>\n" );
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document.write( "2cos^2 (-30°)-1\r<BR>\n" );
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document.write( "a. Use the appropriate&#8203; double-angle formula to rewrite the given expression as the&#8203; sine, cosine, or tangent of the corresponding&#8203; double-angle.<BR>\n" );
document.write( "&#8203;(Do not evaluate. Type your answer in degrees.)\r<BR>\n" );
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document.write( "b.Find the exact value of the trigonometric expression without the use of a calculator.<BR>\n" );
document.write( "&#8203;(Use integers or fractions for any numbers in the expression. Type an exact&#8203; answer, using radicals as&#8203; needed.)\r<BR>\n" );
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document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #715416 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13200)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><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=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=715416\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "(a) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%28cosx%29%5E2-1 ALIGN=MIDDLE  ALT=\"2%28cosx%29%5E2-1\"   DISABLED_style= \"max-width:90%; height:auto;\" > is a double angle formula for cosine; so<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%28cos%28-30%29%29%5E2-1+=+cos%28-60%29 ALIGN=MIDDLE  ALT=\"2%28cos%28-30%29%29%5E2-1+=+cos%28-60%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "(b) -60 degrees is a reference angle of 60 degrees in quadrant IV; cosine is the x value on the unit circle; that is the short leg of a 30-60-90 right triangle; its length is 1/2.<br><BR>\n" );
document.write( "Answer: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2%28cos%28-30%29%29%5E2-1+=+cos%28-60%29+=+1%2F2 ALIGN=MIDDLE  ALT=\"2%28cos%28-30%29%29%5E2-1+=+cos%28-60%29+=+1%2F2\"   DISABLED_style= \"max-width:90%; height:auto;\" > </SPAN>\n" );
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