document.write( "Question 907484: Please help me solve this word problem: Joe is kayaking on a lake. He is 2 miles from the nearest point on the shoreline. From there he is 5 miles from his car. He can average 2 MPH kayaking and 3 MPH walking on the shore. He wishes to get to his car quicker so he heads to the shore at an angle towards his car. \r
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Algebra.Com's Answer #550517 by KMST(5328)\"\" \"About 
You can put this solution on YOUR website!
Joe's kayak is on the lake at point \"K\" (for KAYAK).
\n" ); document.write( "The nearest point on the shore is \"N\" (for NEAREST),
\n" ); document.write( "and Joe's car is next to the shoreline at point \"C\" (for CAR).
\n" ); document.write( "Joe will land the kayak at shoreline point \"L\" (for LANDING),
\n" ); document.write( "which is somewhere between \"N\" and \"C\" ,
\n" ); document.write( "at a distance \"x\" \"miles\" from point \"N\" ,
\n" ); document.write( "at a distance \"h\" (for hypotenuse) from point \"K\",
\n" ); document.write( "and at a distance \"5-x\" from point \"C\" .\r
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\n" ); document.write( "The Pythagorean theorem tells us that
\n" ); document.write( "\"h=sqrt%28x%5E2%2B2%5E2%29=sqrt%28x%5E2%2B4%29\" .
\n" ); document.write( "The time (in hours) for Joe to cover that distance kayaking at 2 MPH is
\n" ); document.write( "\"sqrt%28x%5E2%2B4%29%2F2\" .
\n" ); document.write( "The time (in hours) for Joe to cover the distance \"5-x\" walkking at 3 MPH is
\n" ); document.write( "\"%285-x%29%2F3\"
\n" ); document.write( "The total time (in hours for Joe to go from point \"K\" to point \"C\" is
\n" ); document.write( "\"t%28x%29=sqrt%28x%5E2%2B4%29%2F2%2B%285-x%29%2F3\"
\n" ); document.write( "( \"t\" as a function of \"x\" ).
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\n" ); document.write( "That much you would reason, regardless of your math class level and instructor preferences.
\n" ); document.write( "From this point on, what your instructor wants depends.
\n" ); document.write( "If you are being pushed to use and abuse a graphing calculator, you may be expected to graph the function \"t%28x%29\" and find its minimum.
\n" ); document.write( "If you are studying calculus, you may be expected to calculate the derivative of \"t%28x%29\" to find the point where the derivative is zero and \"t%28x%29\" is minimum:
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\n" ); document.write( "\"dt%2Fdx=0\" ---> \"3x-2sqrt%28x%5E2%2B4%29=0\" ---> \"3x=2sqrt%28x%5E2%2B4%29\" ---> \"9x=4%28x%5E2%2B4%29\" ---> \"9x=4x%5E2%2B16\" ---> \"5x%5E2=16\" ---> \"x%5E2=16%2F5\" ---> \"x=sqrt%2816%2F5%29%7D%7D+---%3E+%7B%7B%7Bx=4%2Fsqrt%285%29=4sqrt%285%29%2F5\"
\n" ); document.write( "So \"highlight%28x=about+1.79%29\" .
\n" ); document.write( "(Joe should aim for landing \"highlight%281.79%29\" miles from point \"N\".
\n" ); document.write( "Now that we have found \"x\" for Joe,
\n" ); document.write( "he has all the side lengths for right triangles \"NKL\" (pictured) and \"NKC\" (imagine it),
\n" ); document.write( "so I would let Joe figure out the angles \"NKL\" , \"NKC\" and \"LKC\"
\n" ); document.write( "that he can use to get going in the right direction.
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