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Differentiation in Polar Coordinates. Lesson 10.7. Review. Relationship of polar and rectangular systems x = r cos θ y = r sin θ Given r = f( θ ), simple to find dr/d θ However, we seek dy/dx . Finding dy/dx. We know r = f( θ ) and y = r sin θ and x = r cos θ Then And .
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Differentiation in Polar Coordinates Lesson 10.7
Review • Relationship of polar and rectangular systems • x = r cos θ y = r sin θ • Given r = f(θ), simple to find dr/dθ • However, we seek dy/dx
Finding dy/dx • We know • r = f(θ) and y = r sin θ and x = r cos θ • Then • And
Finding dy/dx • Since • Then
Example • Given r = cos 3θ • Find the slope of the line tangent at (1/2, π/9) • dy/dx = ? • Evaluate •
Define for Calculator • It is possible to define this derivative as a function on your calculator
Try This! • Find where the tangent line is horizontal for r = 2 cos θ • Find dy/dx • Set equal to 0, solve for θ
Assignment • Lesson 10.7 • Page 443 • Exercises 1 – 21 odd