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  1. AP Calculus
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Define polar coordinates.

A two-dimensional coordinate system defined by a distance (r) from the origin and an angle (θ) from the positive x-axis.

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Define polar coordinates.

A two-dimensional coordinate system defined by a distance (r) from the origin and an angle (θ) from the positive x-axis.

What are polar functions?

Functions graphed in a polar coordinate system using distance (r) from a fixed point (pole) and angle (θ) from the positive x-axis.

Define Cartesian coordinates.

A coordinate system that specifies each point uniquely in a plane by a pair of numerical coordinates, which are the signed distances to the point from two fixed perpendicular directed lines, measured in the same unit of length.

What does drdθ\frac{dr}{d\theta}dθdr​ represent in polar functions?

The rate of change of the distance from the origin with respect to the angle θ. Helps find points furthest or closest to the origin.

What does dydx\frac{dy}{dx}dxdy​ represent for polar functions?

The slope of the tangent line to the polar curve in Cartesian coordinates.

Define the pole in polar coordinates.

The fixed point from which the distance 'r' is measured in a polar coordinate system. It is essentially the origin.

What is the radial component of a polar curve?

The first derivative of r with respect to θ, denoted as r'(θ), representing the instantaneous rate of change of the distance from the origin.

What is radial curvature?

The second derivative of r with respect to θ, denoted as r''(θ), representing the rate of change of the curvature.

Define the angle θ in polar coordinates.

The angle measured counter-clockwise from the positive x-axis to the line connecting the pole to the point.

What are Cartesian equations?

Equations expressed in terms of x and y coordinates, representing relationships between these variables on a Cartesian plane.

Compare converting polar to Cartesian vs. Cartesian to polar.

Polar to Cartesian: Uses x=rcos⁡θx = r\cos\thetax=rcosθ and y=rsin⁡θy = r\sin\thetay=rsinθ to eliminate r and θ. | Cartesian to Polar: Uses r=x2+y2r = \sqrt{x^2 + y^2}r=x2+y2​ and θ=arctan⁡(yx)\theta = \arctan(\frac{y}{x})θ=arctan(xy​) to eliminate x and y.

Compare finding drdθ\frac{dr}{d\theta}dθdr​ vs. dydx\frac{dy}{dx}dxdy​ in polar coordinates.

drdθ\frac{dr}{d\theta}dθdr​: Gives the rate of change of the distance from the origin. | dydx\frac{dy}{dx}dxdy​: Gives the slope of the tangent line in Cartesian coordinates.

Compare the graphs of r=acos⁡(θ)r = a\cos(\theta)r=acos(θ) and r=asin⁡(θ)r = a\sin(\theta)r=asin(θ).

r=acos⁡(θ)r = a\cos(\theta)r=acos(θ): Circle centered on the x-axis. | r=asin⁡(θ)r = a\sin(\theta)r=asin(θ): Circle centered on the y-axis.

Compare limacons with and without inner loops.

With Inner Loop: |a| < |b| in r=a+bcos⁡(θ)r = a + b\cos(\theta)r=a+bcos(θ) or r=a+bsin⁡(θ)r = a + b\sin(\theta)r=a+bsin(θ). | Without Inner Loop: |a| >= |b| in r=a+bcos⁡(θ)r = a + b\cos(\theta)r=a+bcos(θ) or r=a+bsin⁡(θ)r = a + b\sin(\theta)r=a+bsin(θ).

Compare polar coordinates to Cartesian coordinates.

Polar: Uses distance from origin (r) and angle (θ). | Cartesian: Uses horizontal (x) and vertical (y) distances from axes.

Compare the derivatives of r with respect to θ and y with respect to x in polar coordinates.

drdθ\frac{dr}{d\theta}dθdr​: Radial component, rate of change of distance from the origin. | dydx\frac{dy}{dx}dxdy​: Slope of the tangent line in Cartesian coordinates.

Compare using drdθ\frac{dr}{d\theta}dθdr​ to find max/min r values and using dydx\frac{dy}{dx}dxdy​ to find tangent lines.

drdθ\frac{dr}{d\theta}dθdr​ finds where the curve is furthest or closest to the origin. | dydx\frac{dy}{dx}dxdy​ finds the slope of the tangent line at a point on the curve.

Compare the shape of r=acos⁡(nθ)r = a\cos(n\theta)r=acos(nθ) when n is even vs. odd.

n is even: Rose curve with 2n petals. | n is odd: Rose curve with n petals.

Compare the use of sine and cosine in defining polar curves.

Sine: Often associated with vertical symmetry or curves aligned along the y-axis. | Cosine: Often associated with horizontal symmetry or curves aligned along the x-axis.

Compare the graphs of r=a+acos⁡(θ)r = a + a\cos(\theta)r=a+acos(θ) and r=a+asin⁡(θ)r = a + a\sin(\theta)r=a+asin(θ).

Both are cardioids. r=a+acos⁡(θ)r = a + a\cos(\theta)r=a+acos(θ): Symmetric about the x-axis. | r=a+asin⁡(θ)r = a + a\sin(\theta)r=a+asin(θ): Symmetric about the y-axis.

Explain how to convert a polar equation to a Cartesian equation.

Use the relations x=rcos⁡θx = r\cos\thetax=rcosθ, y=rsin⁡θy = r\sin\thetay=rsinθ, and r=x2+y2r = \sqrt{x^2 + y^2}r=x2+y2​ to eliminate r and θ and express the equation in terms of x and y.

Explain how to find points furthest/closest from the origin for a polar function.

Find drdθ\frac{dr}{d\theta}dθdr​, set it equal to zero, solve for θ\thetaθ, and plug the θ\thetaθ values back into the original equation to find the corresponding r values. Also, check endpoints.

Why is it useful to convert polar equations to Cartesian equations?

It allows for easier visualization and graphing on a traditional x-y coordinate plane, especially for complex functions.

Explain the significance of the first derivative of r with respect to θ.

It represents the radial component of the curve and indicates the instantaneous rate of change of the distance from the origin.

Explain the significance of the second derivative of r with respect to θ.

It represents the radial curvature of the curve and indicates the rate of change of the curvature.

What is the relationship between polar and parametric equations?

Polar equations can be expressed parametrically using x=rcos⁡θx = r\cos\thetax=rcosθ and y=rsin⁡θy = r\sin\thetay=rsinθ, where θ\thetaθ is the parameter.

What information does dydx\frac{dy}{dx}dxdy​ provide about a polar curve?

It gives the slope of the tangent line to the curve at a given point in Cartesian coordinates, indicating the direction of the curve at that point.

Why is the chain rule important when finding dydx\frac{dy}{dx}dxdy​ for polar functions?

Because y and x are both functions of r and θ, and r is a function of θ, the chain rule is needed to relate the derivatives.

Describe the process of finding the tangent line to a polar curve at a specific angle.

Calculate dydx\frac{dy}{dx}dxdy​ at the given angle, find the x and y coordinates using x=rcos⁡θx = r\cos\thetax=rcosθ and y=rsin⁡θy = r\sin\thetay=rsinθ, then use the point-slope form to find the equation of the tangent line.

Explain how trigonometric identities are used in polar coordinate problems.

Trigonometric identities are used to simplify expressions, convert between polar and Cartesian coordinates, and solve equations involving trigonometric functions of θ.