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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} 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} 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=rcosθx = r\cos\theta and y=rsinθy = r\sin\theta to eliminate r and θ. | Cartesian to Polar: Uses r=x2+y2r = \sqrt{x^2 + y^2} and θ=arctan(yx)\theta = \arctan(\frac{y}{x}) to eliminate x and y.

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

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

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

r=acos(θ)r = a\cos(\theta): Circle centered on the x-axis. | r=asin(θ)r = a\sin(\theta): 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) or r=a+bsin(θ)r = a + b\sin(\theta). | Without Inner Loop: |a| >= |b| in r=a+bcos(θ)r = a + b\cos(\theta) or r=a+bsin(θ)r = a + b\sin(\theta).

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}: Radial component, rate of change of distance from the origin. | dydx\frac{dy}{dx}: Slope of the tangent line in Cartesian coordinates.

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

drdθ\frac{dr}{d\theta} finds where the curve is furthest or closest to the origin. | dydx\frac{dy}{dx} 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) 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) and r=a+asin(θ)r = a + a\sin(\theta).

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

How to convert r=2sinθr = 2\sin\theta to Cartesian form?

Multiply both sides by r: r2=2rsinθr^2 = 2r\sin\theta. Substitute r2=x2+y2r^2 = x^2 + y^2 and y=rsinθy = r\sin\theta: x2+y2=2yx^2 + y^2 = 2y. Complete the square: x2+(y1)2=1x^2 + (y-1)^2 = 1.

How to find dydx\frac{dy}{dx} for r=θr = \theta?

Find x and y: x=rcosθ=θcosθx = r\cos\theta = \theta\cos\theta, y=rsinθ=θsinθy = r\sin\theta = \theta\sin\theta. Find dxdθ\frac{dx}{d\theta} and dydθ\frac{dy}{d\theta}: dxdθ=cosθθsinθ\frac{dx}{d\theta} = \cos\theta - \theta\sin\theta, dydθ=sinθ+θcosθ\frac{dy}{d\theta} = \sin\theta + \theta\cos\theta. Then, dydx=sinθ+θcosθcosθθsinθ\frac{dy}{dx} = \frac{\sin\theta + \theta\cos\theta}{\cos\theta - \theta\sin\theta}.

How to find points closest/furthest from the origin for r=1+cosθr = 1 + \cos\theta?

Find drdθ=sinθ\frac{dr}{d\theta} = -\sin\theta. Set sinθ=0- \sin\theta = 0, so θ=0,π\theta = 0, \pi. Evaluate r at these points: r(0)=2r(0) = 2, r(π)=0r(\pi) = 0. The closest point is 0, the furthest is 2.

How do you find the equation of the tangent line to r=sin(2θ)r = \sin(2\theta) at θ=π4\theta = \frac{\pi}{4}?

  1. Find x and y in terms of θ: x=rcos(θ)=sin(2θ)cos(θ)x = r\cos(\theta) = \sin(2\theta)\cos(\theta), y=rsin(θ)=sin(2θ)sin(θ)y = r\sin(\theta) = \sin(2\theta)\sin(\theta). 2. Compute dxdθ\frac{dx}{d\theta} and dydθ\frac{dy}{d\theta}. 3. Calculate dydx=dy/dθdx/dθ\frac{dy}{dx} = \frac{dy/d\theta}{dx/d\theta} at θ=π4\theta = \frac{\pi}{4}. 4. Find the (x, y) coordinates at θ=π4\theta = \frac{\pi}{4}. 5. Use the point-slope form to write the equation of the tangent line.

How do you convert the Cartesian equation x2+y2=9x^2 + y^2 = 9 to polar form?

  1. Recall that r2=x2+y2r^2 = x^2 + y^2. 2. Substitute r2r^2 for x2+y2x^2 + y^2 in the given equation. 3. The polar form is r2=9r^2 = 9, which simplifies to r=3r = 3.

How to find the slope of the tangent line to r=2cos(θ)r = 2\cos(\theta) at θ=π3\theta = \frac{\pi}{3}?

  1. Find x and y: x=2cos2(θ)x = 2\cos^2(\theta), y=2cos(θ)sin(θ)=sin(2θ)y = 2\cos(\theta)\sin(\theta) = \sin(2\theta). 2. Find dxdθ=4cos(θ)sin(θ)=2sin(2θ)\frac{dx}{d\theta} = -4\cos(\theta)\sin(\theta) = -2\sin(2\theta) and dydθ=2cos(2θ)\frac{dy}{d\theta} = 2\cos(2\theta). 3. Calculate dydx=2cos(2θ)2sin(2θ)=cot(2θ)\frac{dy}{dx} = \frac{2\cos(2\theta)}{-2\sin(2\theta)} = -\cot(2\theta). 4. Evaluate at θ=π3\theta = \frac{\pi}{3}: dydx=cot(2π3)=33\frac{dy}{dx} = -\cot(\frac{2\pi}{3}) = \frac{\sqrt{3}}{3}.

How do you find the x-coordinate of a point on the polar curve r=4sin(θ)r = 4\sin(\theta) when θ=π6\theta = \frac{\pi}{6}?

  1. Calculate r: r=4sin(π6)=412=2r = 4\sin(\frac{\pi}{6}) = 4 * \frac{1}{2} = 2. 2. Use the formula x=rcos(θ)x = r\cos(\theta): x=2cos(π6)=232=3x = 2\cos(\frac{\pi}{6}) = 2 * \frac{\sqrt{3}}{2} = \sqrt{3}.

How do you find the y-coordinate of a point on the polar curve r=2+cos(θ)r = 2 + \cos(\theta) when θ=π2\theta = \frac{\pi}{2}?

  1. Calculate r: r=2+cos(π2)=2+0=2r = 2 + \cos(\frac{\pi}{2}) = 2 + 0 = 2. 2. Use the formula y=rsin(θ)y = r\sin(\theta): y=2sin(π2)=21=2y = 2\sin(\frac{\pi}{2}) = 2 * 1 = 2.

How do you determine the values of θ\theta where the polar curve r=3sin(θ)r = 3\sin(\theta) intersects the x-axis?

  1. The x-axis corresponds to y=0y = 0. 2. Set y=rsin(θ)=0y = r\sin(\theta) = 0. 3. This implies sin(θ)=0\sin(\theta) = 0 (since r is not always zero). 4. Solve for θ\theta: θ=nπ\theta = n\pi, where n is an integer.

How do you determine the values of θ\theta where the polar curve r=2cos(θ)r = 2\cos(\theta) intersects the y-axis?

  1. The y-axis corresponds to x=0x = 0. 2. Set x=rcos(θ)=0x = r\cos(\theta) = 0. 3. This implies cos(θ)=0\cos(\theta) = 0 (since r is not always zero). 4. Solve for θ\theta: θ=π2+nπ\theta = \frac{\pi}{2} + n\pi, where n is an integer.