document.write( "Question 820437: In each case, find sin(a), cos(a), csc(a), sec(a), and cot(a). Note: 'a' means alpha.\r
\n" ); document.write( "\n" ); document.write( "45. cos(2a)=3/5 and 0°<2a<90°\r
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\n" ); document.write( "\n" ); document.write( "I've been trying to figure out this problem for some time, but I need help. \n" ); document.write( "
Algebra.Com's Answer #493539 by stanbon(75887)\"\" \"About 
You can put this solution on YOUR website!
In each case, find sin(a), cos(a), csc(a), sec(a), and cot(a). Note: 'a' means alpha.
\n" ); document.write( "45. cos(2a)=3/5 and 0°<2a<90°
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\n" ); document.write( "cos = x/r
\n" ); document.write( "If cos(2a) = 3/5, x = 3 and r = 5
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\n" ); document.write( "Then y = sqrt[5^2-3^2] = sqrt[16] = 4
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\n" ); document.write( "And sin(2a) = y/r = 4/5
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\n" ); document.write( "Now use the half-angle formulas to get:
\n" ); document.write( "sin(2a/2) = sqrt[(1-cos(2a)/2] = sqrt[(1-(3/5))/2] = sqrt[1/5] = (1/5)sqrt(5)
\n" ); document.write( "cos(2a/2) = sqrt[(1+cos(2a)/2] = sqrt[(1+(3/5))/2] = sqrt(4/5) = (2/5)sqrt(5)
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\n" ); document.write( "tan(2a/2) = sin(2a/2)/cos(2a/2) = 1/2
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\n" ); document.write( "Note: csc(a), sec(a), cot(a) are the inverse of above.
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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