document.write( "Question 1036508: I am really having a hard time with this one. Been working on it for nearly 3 hours and cant seem to figure out how to make it work.\r
\n" ); document.write( "\n" ); document.write( "Problem: r(t) is the position of a particle in the xy-plane at time t. Find an equation in x and y whose graph is the path of the particle. Then find the particle’s velocity and acceleration vectors at the given value of t.\r
\n" ); document.write( "\n" ); document.write( "\"+r%28t%29+=+e%5Et+i+%2B+%282%2F9%29+e%5E%282t%29+j+\"
\n" ); document.write( "where \"+t+=+ln3+\"\r
\n" ); document.write( "\n" ); document.write( "To find the Equation, I first organize it into a set:
\n" ); document.write( "[ \"+e%5Et+\", \"+%282%2F9%29+e%5E%282t%29+\" ]
\n" ); document.write( "Then I just plug in the value of t (ln3)
\n" ); document.write( "[ \"+e%5E%28ln3%29+\", \"+%282%2F9%29+e%5E%282%28ln3%29%29+\" ]
\n" ); document.write( "I then reconstruct the original problem with the new values:
\n" ); document.write( "\"+r%28t%29+=+e%5E%28ln3%29+i+%2B+%282%2F9%29+e%5E%282%28ln3%29%29+j+\"
\n" ); document.write( "\"+r%28ln3%29+=+e%5E%281.0986%29+i+%2B+%282%2F9%29+e%5E%282.1972%29+j+\"
\n" ); document.write( "then I change the i / j coordinates to x/y coordinates
\n" ); document.write( "\"+r%28ln3%29+=+e%5E%281.0986%29+x+%2B+%282%2F9%29e%5E%282.1972%29+y+\"
\n" ); document.write( "-----------------------------\r
\n" ); document.write( "\n" ); document.write( "As for velocity and acceleration, so far I have figured it like this:
\n" ); document.write( "Velocity:
\n" ); document.write( "[ \"+e%5Et+\", \"+%282%2F9%29+e%5E%282t%29+\" ]
\n" ); document.write( "[ \"+te+\", \"+%284%2F9%29+e%5Et+\" ]
\n" ); document.write( "\"+Velocity+=+tei+%2B+%284%2F9%29etj+\"\r
\n" ); document.write( "\n" ); document.write( "Acceleration:
\n" ); document.write( "[ \"+e+\", \"+%284%2F9%29+te+\"]
\n" ); document.write( "\"+Acceleration+=+tei+%2B+%284%2F9%29+tej+\"\r
\n" ); document.write( "\n" ); document.write( "Am I taking the derivative correctly? As far as I know, e remains as e, even after the derivative, right?\r
\n" ); document.write( "\n" ); document.write( "thanks in advance
\n" ); document.write( "

Algebra.Com's Answer #651227 by robertb(5830)\"\" \"About 
You can put this solution on YOUR website!
I think you meant \"+r%28t%29+=+e%5Et%2A+i+%2B+%282%2F9%29+e%5E%282t%29%2A+j+\", which is a vector-valued function.
\n" ); document.write( "Let \"x+=+e%5Et\" and \"y+=+%282%2F9%29+e%5E%282t%29\" as they were meant to be.\r
\n" ); document.write( "\n" ); document.write( "Then after a simple substitution, you should get \"y=%282%2F9%29+%28e%5Et%29%5E2+=+%282%2F9%29x%5E2\".\r
\n" ); document.write( "\n" ); document.write( "\"+Velocity+=+e%5Et%2Ai+%2B+%284%2F9%29e%5E%282t%29%2Aj+\"\r
\n" ); document.write( "\n" ); document.write( "\"+Acceleration+=+e%5Et%2Ai+%2B+%288%2F9%29e%5E%282t%29%2Aj+\"
\n" ); document.write( "
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