00:04
Okay, this question gives you x equals e to the t, y equals e to the negative t, and they want the equation of a tangent line to the curve at t equals 1.
00:14
To find an equation of a tangent line, i need a point and a slope.
00:22
The point will be x equals e to the 1 and y equals e to the negative 1.
00:30
The slope will be dy, dt, divided by dx, dt at t equals 1.
00:39
So, d, y, dt over dxdt is negative e to the negative t divided by e to the t, which is negative e to the negative 2t.
01:01
And at t equals 1, i get negative e to the negative 2.
01:07
So y equals y1 plus the slope times x minus x1.
01:18
There's my equation of the tangent line.
01:22
Now that wasn't a great vertical line.
01:30
Now they want me to remove the parameter and see what i get...