document.write( "Question 821069: lighthouse is 10 km northwest of dock. A ship leaves the dock at 9 am and steams west at 12 kph. at what time will it be 8 km from the lighthouse \n" ); document.write( "
Algebra.Com's Answer #493885 by TimothyLamb(4379)\"\" \"About 
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\n" ); document.write( "LH:
\n" ); document.write( "adj = hyp cos( 45 )
\n" ); document.write( "x = 10 cos( 45 )
\n" ); document.write( "x = 7.0711
\n" ); document.write( "opp = hyp sin( 45 )
\n" ); document.write( "y = 10 cos( 45 )
\n" ); document.write( "y = 7.0711
\n" ); document.write( "LH point: (7.0711, 7.0711)
\n" ); document.write( "---
\n" ); document.write( "ship at 8 km from LH
\n" ); document.write( "point = (x, 0)
\n" ); document.write( "---
\n" ); document.write( "distance formula when ship is at 8 km from LH
\n" ); document.write( "8 = sqrt( (x - 7.0710678)(x - 7.0710678) + (0 - 7.0710678)(0 - 7.0710678) )
\n" ); document.write( "8 = sqrt( (xx - 14.142136x + 50) + 50 )
\n" ); document.write( "64 = xx - 14.142136x + 100
\n" ); document.write( "xx - 14.142136x + 36
\n" ); document.write( "---
\n" ); document.write( "the above quadratic equation is in standard form, with a=1, b=-14.142136, and c=36
\n" ); document.write( "---
\n" ); document.write( "to solve the quadratic equation, by using the quadratic formula, copy and paste this:
\n" ); document.write( "1 -14.142136 36
\n" ); document.write( "into this solver: https://sooeet.com/math/quadratic-equation-solver.php
\n" ); document.write( "---
\n" ); document.write( "the two real roots (i.e. the two x-intercepts), of the quadratic are:
\n" ); document.write( "x = 10.8127257
\n" ); document.write( "x = 3.32941026
\n" ); document.write( "---
\n" ); document.write( "distance: 8 km from LH when 3.33 km from the dock (along the ship's west course)
\n" ); document.write( "time = 3.33/12 = 0.2775 * 60 = 16.65 min
\n" ); document.write( "---
\n" ); document.write( "answer:
\n" ); document.write( "at 9:17 AM the ship is 8 km from the lighthouse
\n" ); document.write( "---
\n" ); document.write( "Solve and graph linear equations:
\n" ); document.write( "https://sooeet.com/math/linear-equation-solver.php
\n" ); document.write( "---
\n" ); document.write( "Solve quadratic equations, quadratic formula:
\n" ); document.write( "https://sooeet.com/math/quadratic-formula-solver.php
\n" ); document.write( "---
\n" ); document.write( "Solve systems of linear equations up to 6-equations 6-variables:
\n" ); document.write( "https://sooeet.com/math/system-of-linear-equations-solver.php \n" ); document.write( "
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