Finding an Equation for a Perpendicular Line to a Tangent at a Given Point

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SUMMARY

The discussion focuses on finding the equation of a line perpendicular to the tangent of the curve defined by the equation y=x^3-4x+1 at the point (2,1). The derivative of the curve is calculated as y' = 3x^2 - 4, yielding a slope of 8 at x=2. The tangent line is determined to be y=8x-15. The correct perpendicular line, which must pass through the point (2,1), is derived as y=-x/8 + 5/4, correcting the initial miscalculation of the y-intercept.

PREREQUISITES
  • Understanding of calculus, specifically derivatives and slopes of curves
  • Familiarity with the point-slope form of a linear equation
  • Knowledge of perpendicular lines and their slopes
  • Basic algebra skills for manipulating equations
NEXT STEPS
  • Study the concept of derivatives in calculus, focusing on applications in finding tangents
  • Learn about the point-slope form of linear equations and how to apply it
  • Explore the relationship between slopes of perpendicular lines
  • Practice solving problems involving tangent and normal lines to curves
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Students studying calculus, particularly those focusing on derivatives and their applications in geometry, as well as educators looking for examples of tangent and perpendicular lines.

Willowz
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Homework Statement


Find an equation for the line perpendicular to the tangent to the curve y=x^3-4x+1 at the point (2,1).

Homework Equations


point slope form, m * (-1/m) = -1

The Attempt at a Solution


Derivate: y+3x^2-4
m=8 at x=2
Tangent line: y=8x-15
Answer: y=-x/8-15

Answer in book, y=-x/8 + 5/4

Where'd I go wrong?
 
Last edited:
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Hi Willowz! :smile:

Your line has to contain the point (2,1).
For the perpendicular line this means you get another y-intercept than the tangent line has.
 

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