document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1176366>Question 1176366</A>: <I><SPAN STYLE=\"word-break: break-all;\"> For an angle a in the interval [0,π2) it is given that sin(a)=4/5<BR>\n" );
document.write( "Determine cos(a) exactly.\r<BR>\n" );
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document.write( "From my understanding, the angles is in the first quadrant (0 -> 90 deg), but I don't understand, it there a formula I can use?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #803151 by </B><A HREF=/tutors/aboutme.mpl?userid=htmentor><B>htmentor(1343)</B></A><img src=\"/images/stars/stars-12.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=htmentor><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=htmentor><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=803151\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Consider the unit circle, with radius = 1. A point on the unit circle has<BR>\n" );
document.write( "coordinates (x,y). Then sin(a) = y/r = y/1 = y, and cos(a) = x/r = x.<BR>\n" );
document.write( "From the Pythagorean theorem, we know that x^2 + y^2 = r^2 = 1<BR>\n" );
document.write( "If sin(a) = 4/5, we can find cos(a) which is equal to x:<BR>\n" );
document.write( "1 - (4/5)^2 = x^2 -> x = sqrt(9/25) = 3/5<BR>\n" );
document.write( "cos(a) = 3/5 </SPAN>\n" );
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