How do I finish this polar equations problem?

In summary, to convert a polar equation into rectangular form, you can use the equations x = r * cos(theta) and y = r * sin(theta). To graph a polar equation, you can convert it into rectangular form and plot the points. The variable "r" in a polar equation represents the distance from the origin to a point on the graph. To find the domain and range of a polar equation, you can use intervals for theta and r. Most scientific calculators also have a "polar" mode for solving polar equations.
  • #1
shreddinglicks
214
6

Homework Statement



Find the points on the given curve where the tangent is horizontal or vertical

Homework Equations



r = 3cos(θ)

The Attempt at a Solution



d/dθ = -3sin(θ)

for horizontal:

-3sin(θ)sin(θ) + 3cos(θ)cos(θ)

I used identity and got:

3cos(2θ) = 0

I got the values PI/4, 3PI/4

How do I get the values 3/sqrt(2) and -3/sqrt(2)

to give me points (3/sqrt(2), Pi/4) and (-3/sqrt(2), Pi/4)
 
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  • #2
You found some values for ##\theta##. Use the equation you started with to get the corresponding values for ##r##.
 

Related to How do I finish this polar equations problem?

1. How do I convert a polar equation into rectangular form?

To convert a polar equation into rectangular form, we can use the following equations:
x = r * cos(theta) and y = r * sin(theta).
Simply plug in the values for r and theta from the polar equation into these equations to get the corresponding x and y values in rectangular form.

2. How do I graph a polar equation?

To graph a polar equation, we can use the following steps:
1. Convert the polar equation into rectangular form.
2. Plot the points using the x and y values from the rectangular form.
3. Connect the points to create the graph.

3. What does the variable "r" represent in a polar equation?

In a polar equation, the variable "r" represents the distance from the origin to a point on the graph. It is also known as the radius or magnitude.

4. How do I find the domain and range of a polar equation?

The domain of a polar equation is the set of all possible values for theta. It is typically given as an interval, such as [0, 2pi]. The range of a polar equation is the set of all possible values for r. It is also given as an interval, such as [0, infinity).

5. Can I solve a polar equation using a calculator?

Yes, most scientific calculators have a "polar" mode that allows you to enter and solve polar equations. Simply switch to this mode and input the equation using the appropriate variables.

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