Graph $r(t)$ for t = $\pi/4$: Position and Tangent Vectors

In summary, the conversation is about finding the position and tangent vectors for the equation $r(t)=sin(t)$i $+ 2cos(t)$j at $t= \pi/4$ and graphing the original equation, which is an ellipse/circle with bounds from -1 to 1 on the x-axis and -2 to 2 on the y-axis. The position vector at $t=\pi/4$ is $\left\langle \frac{\sqrt{2}}{2}, \sqrt{2} \right\rangle$ and the tangent vector is $\left\langle \frac{\sqrt{2}}{2}, - \sqrt{2} \right\rangle$.
  • #1
ineedhelpnow
651
0
$r(t)=sin(t)$i $+ 2cos(t)$j
$t= \pi/4$

sketch the position vector and the tangent vector

$r'(t)=cos(t)$i $- 2sin(t)$j

$r(\pi/4)= \frac{\sqrt{2}}{2}$i $+ \sqrt{2}$j

$r'(\pi/4)= \frac{\sqrt{2}}{2}$i $- \sqrt{2}$j

$\left\langle \frac{\sqrt{2}}{2}, \sqrt{2} \right\rangle$
$\left\langle \frac{\sqrt{2}}{2}, - \sqrt{2} \right\rangle$

can someone help me graph these. the original equation is the graph of a ellipse/circle from -1 to 1 on the x-axis and -2 to 2 on the y axis
 
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  • #2
ineedhelpnow said:
$r(t)=sin(t)$i $+ 2cos(t)$j
$t= \pi/4$

sketch the position vector and the tangent vector

$r'(t)=cos(t)$i $- 2sin(t)$j

$r(\pi/4)= \frac{\sqrt{2}}{2}$i $+ \sqrt{2}$j

$r'(\pi/4)= \frac{\sqrt{2}}{2}$i $- \sqrt{2}$j

$\left\langle \frac{\sqrt{2}}{2}, \sqrt{2} \right\rangle$
$\left\langle \frac{\sqrt{2}}{2}, - \sqrt{2} \right\rangle$

can someone help me graph these. the original equation is the graph of a ellipse/circle from -1 to 1 on the x-axis and -2 to 2 on the y axis

Let's see...

[desmos="-4,4,-3,3"]x^2+y^2/4=1;y=2x\left\{0<x<\frac{\sqrt{2}}{2}\right\};y=2\sqrt{2}-2x\left\{\frac{\sqrt{2}}{2}<x<\sqrt{2}\right\}[/desmos]
 
  • #3
ok so i literally posted this question on a bunch of different sites and once again MHB was the first to succeed :) thanks ILS!
 

FAQ: Graph $r(t)$ for t = $\pi/4$: Position and Tangent Vectors

What does the graph of r(t) for t = π/4 represent?

The graph of r(t) for t = π/4 represents the position of an object at a specific time, t = π/4, in a two-dimensional coordinate system.

How is the position of the object determined on the graph?

The position of the object is determined by the coordinates of the point on the graph at t = π/4. The x-coordinate represents the horizontal position and the y-coordinate represents the vertical position.

What is the significance of the tangent vector on the graph?

The tangent vector on the graph represents the direction and magnitude of the velocity of the object at t = π/4. It is tangent to the curve at that point and points in the direction of the object's motion.

How is the tangent vector calculated for a given point on the graph?

The tangent vector can be calculated by finding the derivative of r(t) and plugging in t = π/4. This will give the slope of the tangent line, which can then be used to determine the direction and magnitude of the vector.

Can the position and tangent vectors on the graph change over time?

Yes, the position and tangent vectors on the graph can change over time as the object moves. The graph of r(t) for t = π/4 represents a specific moment in time, but the position and tangent vectors will change as time progresses.

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