Exploring Functions with Polynomial Parameterization
Discover how to parameterize functions, find tangent lines, and explore circles using polynomial equations. Learn to apply trigonometry to find angles and use derivatives for tangent lines.
Exploring Functions with Polynomial Parameterization
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Presentation Transcript
Looking closely at a function Chapter 9
Quick Review of Parameterization y = 3x2 + 4x + 5 Point P(6,2) x = 6 + u y = 2 + v 2 + v = 3 (6 + u)2 + 4(6 + u) + 5 2 + v = 3 (36 +12u + u2) + 24 + 4u + 5 2 + v = 108 +36u + 3u2+ 24 + 4u + 5 2 + v = 108 +36u+ 3u2+ 24 +4u + 5 v = 135 + 40u + 3u2 x -6 = u y - 2 = v y – 2 = 135 + 40 (x - 6) + 3 (x2 – 12x + 36) ....
Linear Approximation using Polynomial Parameterization (1,2) y = 4x2 - 2
y = 4x2 – 2 (1,2) • What do we do first parameterize the function?
Now how about a circle… • x2 + y2 = 25 • What is the equation of the tangent line at (3,4)
Now how about a circle… • x2 + y2 = 25 (3,4)
Writing the equation of a line… • What do you need to know? • Then what do you do?
Find the tangent line when x = -2 • y = 2x2 + 3x + 1
Find the tangent line when x = -2 • y = 2x2 + 3x + 1 if x = -2 • y = 2(-2)2 + 3(-2) + 1 • y = 8 – 6 + 1 • y = 3 (-2, 3) x = u – 2 y = v + 3 • v + 3 = 2(u - 2)2 + 3(u – 2) + 1 • v + 3 = 2u2 – 8u + 8 + 3u – 6 + 1 • v = -5u + 2u2 • y – 3 = -5 (x + 2) • y = -5x - 7
y • As indicated in the diagram (which is not to scale) the tangent line to the graph of f(x) = x2+5x-24 at x = 12 meets the x-axis at an angle AOB whose tangent is . The angle AOB measures radians.
Use trigonometry... • What do you need to use trig? • How can you find it given this situation?
Looking at the tangent line... • f(x) = x2+5x-24 • at x = 12 • What information can you find using this...
Looking at the tangent line... • f(x) = x2+5x-24 • at x = 12 • Find the tangent line
Looking at the tangent line... • f(12) = x2+5x-24 • f(12) = (12)2+5(12)-24 • f(12) = 144 + 70 – 24 • f(12) = 190 • A(12,190)
Using parameters... f(x) = x2+5x-24 A(12,190) x=12+u y=190+v • 190+v= (12+u)2+5(12+u)-24 • 190+v=144+24u+u2+70+5u-24 • v-29u-u2=0 x - 12=u y- 190=v
Using parameters... • v-29u-u2=0 • y – 190 – 29(x-12) = 0 • y – 190 – 29x + 348=0 • y = 29x - 158 x-12=u y-190=v
Using parameters... • v-29u-u2=0 • y – 190 – 29(x-12) = 0 • y – 190 – 29x + 348=0 • y = 29x - 158 - 158 x-12=u y-190=v
Looking at the tangent line... Diagram is not to scale. Now what do you know? (12,190) - 158
Looking at the tangent line... Diagram is not to scale. (12,190) 348 - 158 12
Looking at the tangent line... Diagram is not to scale. Now you have 2 sides – you can find the desired angle. (12,190) 348 - 158 12
Looking at the tangent line... Diagram is not to scale. tan q = 348/12 (must find degree to change to radians) tan q = tan-1(348/12) . . . (12,190) 348 - 158 12
Another way to find the tangent line? • Derivative? • What is the Derivative?