document.write( "Question 623198: Find the exact value of sin θ, if cos θ = 4/5 and θ lies in quadrant IV. \n" ); document.write( "

Algebra.Com's Answer #391951 by Alan3354(69443) $\"\"$ $\"About$

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Find the exact value of sin θ, if cos θ = 4/5 and θ lies in quadrant IV.
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\n" ); document.write( "Plot the terminal point on the x-y grid
\n" ); document.write( "x = 4, r = 5
\n" ); document.write( "y = 3 (by Pythagoras) --> -3 in Q4
\n" ); document.write( "sin = y/r
\n" ); document.write( "sin = -3/5
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\n" ); document.write( "Or do it this way:
\n" ); document.write( "sin^2 + cos^2 = 1
\n" ); document.write( "sin = sqrt(1 - cos^2) = 3/5 or -3/5
\n" ); document.write( "Q4 --> -3/5
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