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  1. AP Pre Calculus
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What are the differences between Cartesian and Polar coordinates?

Cartesian: Uses (x, y), rectangular grid | Polar: Uses (r, θ), circular grid.

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What are the differences between Cartesian and Polar coordinates?
Cartesian: Uses (x, y), rectangular grid | Polar: Uses (r, θ), circular grid.
Compare the graphs of y = x and r = θ.
y = x: Straight line | r = θ: Spiral.
Compare the equations for a circle in Cartesian and Polar form.
Cartesian: (x-h)² + (y-k)² = r² | Polar: r = a (centered at origin).
Compare symmetry about the x-axis in Cartesian and Polar coordinates.
Cartesian: Replace y with -y | Polar: Replace θ with -θ.
Compare symmetry about the y-axis in Cartesian and Polar coordinates.
Cartesian: Replace x with -x | Polar: Replace θ with π - θ.
Compare the effect of changing 'a' in r = a cos(θ) and r = cos(aθ).
r = a cos(θ): Changes diameter of circle | r = cos(aθ): Changes the number of 'petals'.
Compare the concept of periodicity in Cartesian and Polar functions.
Cartesian: f(x) = f(x + p) | Polar: f(θ) = f(θ + 2π) (typically).
Compare the representation of the origin in Cartesian and Polar coordinates.
Cartesian: Unique representation (0,0) | Polar: Infinite representations (0, θ) for any θ.
Compare graphing a line in Cartesian (y = mx + b) and Polar coordinates.
Cartesian: Straight line | Polar: Requires converting to polar equation, can be more complex.
Compare the area calculation for a region in Cartesian and Polar coordinates.
Cartesian: ∫∫ dxdy | Polar: ∫∫ r dr dθ
Define polar coordinates.
A system using (r, θ) to locate points, where r is the distance from the origin and θ is the angle from the positive x-axis.
What is a polar function?
An equation in the form r = f(θ), where θ is the input angle and r is the output distance from the origin.
Define symmetry about the origin in polar functions.
A polar function is symmetric about the origin if its graph is unchanged when rotated by 180 degrees.
What is periodicity in polar functions?
A polar function is periodic if its graph repeats after a fixed interval of θ.
Define 'r' in polar coordinates.
The distance from the origin (0,0) to the point in the polar plane.
Define 'θ' in polar coordinates.
The angle measured counterclockwise from the positive x-axis to the point in the polar plane.
What is a cardioid?
A heart-shaped polar curve, often represented by the equation r = a(1 ± cos θ) or r = a(1 ± sin θ).
What is a lemniscate?
A figure-eight-shaped polar curve, often represented by the equation r² = a²cos(2θ) or r² = a²sin(2θ).
What does a negative 'r' value signify in polar coordinates?
It indicates a point located in the opposite direction of the angle θ from the origin.
What is the polar equation of a circle centered at the origin?
r = a, where 'a' is the radius of the circle.
How do you graph r = 2cos(θ)?
1. Create a table of θ and r values. 2. Plot the points (r, θ). 3. Connect the points to form a circle.
How do you determine the symmetry of r = f(θ)?
1. Test for x-axis symmetry by replacing θ with -θ. 2. Test for y-axis symmetry by replacing θ with π - θ. 3. Test for origin symmetry by replacing r with -r.
How do you convert (2, π/3) from polar to Cartesian coordinates?
1. Use x = r cos(θ) and y = r sin(θ). 2. x = 2 cos(π/3) = 1. 3. y = 2 sin(π/3) = √3. 4. Cartesian coordinates are (1, √3).
How do you convert (1, 1) from Cartesian to polar coordinates?
1. Use r = √(x² + y²) and θ = arctan(y/x). 2. r = √(1² + 1²) = √2. 3. θ = arctan(1/1) = π/4. 4. Polar coordinates are (√2, π/4).
How do you find the period of r = sin(2θ)?
1. Determine the period of the trigonometric function. 2. Period of sin(2θ) is π. 3. The period of the polar function is π.
How do you find the area enclosed by the polar curve r = 2cos(θ)?
1. Identify the limits of integration (0 to π). 2. Use the formula A = (1/2) ∫ [r(θ)]² dθ. 3. A = (1/2) ∫ (2cos(θ))² dθ from 0 to π. 4. Evaluate the integral to find the area.
How do you find the points of intersection between r = sin(θ) and r = cos(θ)?
1. Set the two equations equal to each other: sin(θ) = cos(θ). 2. Solve for θ: θ = π/4, 5π/4. 3. Find the corresponding r values. 4. The points of intersection are (√2/2, π/4) and (-√2/2, 5π/4).
How do you graph a cardioid r = 1 + cos(θ)?
1. Create a table of θ and r values for key angles (0, π/2, π, 3π/2, 2π). 2. Plot the points on the polar plane. 3. Connect the points to form the heart-shaped curve.
How do you determine if a polar curve is symmetric about the x-axis?
1. Replace θ with -θ in the equation. 2. If the equation remains unchanged, the curve is symmetric about the x-axis.
How do you find the maximum value of r for the polar function r = 3sin(θ)?
1. Find the maximum value of the trigonometric function. 2. The maximum value of sin(θ) is 1. 3. Therefore, the maximum value of r is 3.