Tangent line Definition and 279 Threads

In geometry, the tangent line (or simply tangent) to a plane curve at a given point is the straight line that "just touches" the curve at that point. Leibniz defined it as the line through a pair of infinitely close points on the curve. More precisely, a straight line is said to be a tangent of a curve y = f(x) at a point x = c if the line passes through the point (c, f(c)) on the curve and has slope f'(c), where f' is the derivative of f. A similar definition applies to space curves and curves in n-dimensional Euclidean space.
As it passes through the point where the tangent line and the curve meet, called the point of tangency, the tangent line is "going in the same direction" as the curve, and is thus the best straight-line approximation to the curve at that point.
The tangent line to a point on a differentiable curve can also be thought of as the graph of the affine function that best approximates the original function at the given point.Similarly, the tangent plane to a surface at a given point is the plane that "just touches" the surface at that point. The concept of a tangent is one of the most fundamental notions in differential geometry and has been extensively generalized; see Tangent space.
The word "tangent" comes from the Latin tangere, "to touch".

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  1. P

    Implicit Differentiation - Tangent Line & Horizontal Tangents

    Homework Statement Find an equation of the tangent line to this curve at the point (1, -2). Homework Equations The Attempt at a Solution 2y' = 3x^2+6x y' = 3x^2+6x y'=3/2x^2+3x y+2=3(x-1) y+2=3x-3 y=3x-5
  2. L

    Slope of Tangent Line for g(x)=x^2-4 at (1,-3) | Calculus Homework Solution

    Homework Statement find the slope of the tangent line whose g(x)=x^2-4 at point (1,-3) Homework Equations lim f(x+Δχ) -F(c)/ (Δχ) The Attempt at a Solution g(x)= x^2-4 G(1+Δχ)= (1+Δχ)^2-4 ==> Δχ^2+2Δχ-3 lim (Δχ^2+2Δχ-3) - (-3)/(Δχ) = 0 but in the book the answer is 2 so what...
  3. C

    Parameterized tangent line to a parameterized curve

    Homework Statement I seem to remember that a parameterized a(t) curve in \mathbb{R}^3 that one can construct the tangent from the slope of a'(t) and the curve itself. such that the tangent line L = a(t) + s * a'(t) to a. This is supposedly a straight line in \mathbb{R}^3. To make a...
  4. P

    If the tangent line to y = f (x) at (9,7) passes through the point (0,6)

    Homework Statement If the tangent line to y = f (x) at (9,7) passes through the point (0,6), find the following. (a) f (9) (b) f ' (9) Homework Equations f '(x) = f(x+h) - f(x)/h ? The Attempt at a Solution I really have no idea how to even begin going about this one, so a...
  5. D

    Equation of a tangent line given x

    I am having a time trying to figure out this problem given only an x value. The equation is "Find the equation of the tangent line to y= Square root of x^4-2337 ...at x=7. If anybody could help me solve this it would be a great help. Thanks
  6. A

    An Unknown Conic and Equation of Tangent Line HELP

    An Unknown Conic and Equation of Tangent Line **HELP** Homework Statement (a) Find the positive y-coordinate of the point on the conic whose x-coordinate is 27cos\theta, where 0<\theta<\pi/2 (b) The slope of the tangent line to the conic through the point (27cos\theta, y1) is -1/27cot\theta...
  7. S

    Finding the Vertical Tangent Line of x3 + xy - y2 = 10 Curve

    The curve defined by x3 +xy - y2 = 10 has a vertical tangent line when x = ? To find when the tangent line is vertical, could I find when the slope is undefined for the original function? The way I previously tried this problem was by taking the first derivative and then finding when x = 0...
  8. M

    Find the equation of the tangent line

    Homework Statement Find the equation of the tangent line to the curve 3xy = x^3 + y^3 at point (2/3,4/3) Homework Equations The Attempt at a Solution I found the deriviative to be 3x^2-3y / 3x - 3y^2 which i simplified to x^2 - y / x - y^2 I found the slope of at those...
  9. J

    Find the tangent line between two surfaces

    Homework Statement Let C be the intersection of the two surfaces: S1: x^2 + 4y^2 + z^2 = 6; s2: z = x^2 + 2y; Show that the point (1, -1, -1) is on the curve C and find the tangent line to the curve C at the point (1, -1, -1). Homework Equations partial derivates, maybe the gradient...
  10. K

    Equation for Tangent Line to Inverse Function at (3,1) of f(x)=x^3+2x^2-x+1

    Homework Statement Find an equation for the line tangent to to the graph of f^-1 at the pt (3,1) if f(x)=x^3+2x^2-x+1 Homework Equations The Attempt at a Solution I used the Inverse Function Thm 1/(3x^2+4x) Now do I plug in 3 to this to find slope? 1/21 y-1=1/21(x-3)...
  11. G

    Finding parametric equations of a tangent line

    Homework Statement Find parametric equations of the tangent line at the point (-2,2,4) to the curve of intersection of the surface z=2x2-y2 and the plane z=4 Homework Equations Not sure The Attempt at a Solution Not sure quite how to approach this. take the gradient of...
  12. 1

    Find an equation of the tangent line

    Homework Statement Find an Equation of the tangent line to the curve y=10^x at the point (1,10) Homework Equations Derivative y=mx+b The Attempt at a Solution I am totally lost I don't know what to do with 10^x Please help me this will save me failing the class
  13. M

    Points where tangent line touches 2 circles

    Homework Statement On the circles y^2+x^2=1 and y^2+(x-3)^2=4 There is a line with positive slope that is tangent to both circles. Determine the points at which this tangent touches each circle. Homework Equations the derivative of the first circle i found: y'=-x/y the derivative of...
  14. A

    Quick Tangent Line Approximation (Derivatives)

    Homework Statement The tangent line through given points (pi/4,pi/4) m=1 y= cos(y)cos(x)/sin(x)sin(y) The Attempt at a Solution dy/dx= d/dx[cos(y)cos(x)/sin(x)sin(y)] First use quotient rule ? vu'-uv'/v^2 v= sin(x)sin(y) v'= do i need to use product rule? for product rule...
  15. M

    How do I find the slope of the tangent line using Definition 1 and Equation 2?

    Homework Statement Find the slope of the tangent line to the curve y=x3 at point (-1,-1) (i) Using Definition 1 m=limx-->a\frac{f(x)-f(a)}{x-a} (i) Using Equation 2 m=limh-->0\frac{f(a+h)-f(a)}{h} Homework Equations The Attempt at a Solution For the first one, I got as far...
  16. B

    Solving Tangent Line Problem: Adding & Subtracting 5 Explained

    Homework Statement Ok, how do i solve this question I've attached the picture.. The answer is A but i don't understand how to get that... The Attempt at a Solution The solution is also given , but i don't understand the adding and subtracting 5. the Derivative of y=ln (e^x + 5) y'=...
  17. U

    How Do I Simplify a Fraction Within a Fraction?

    Find the slope of the functions graph at the given point. F(x) = x / x-2 point (3,3) f(x+h) - f(x) / h is what we have to use to find the answer. so I've plugged it all in and have came to this.. ((3+h) / (3+h-2)) - 3 / h I need some help with my simplification...
  18. R

    Find Tangent Line to Path: x(t)=4costi-3sintj+5tk, t=\pi/3

    Find an equation for the line tangent to the given path at the indicated value for the parameter. x(t)=4costi-3sintj+5tk, t=\pi/3 So what I did here was take x'(t) and then plugged in \pi/3 after that to get an equation containing i, j, and k. x'(t)= -4sinti-3costj+5k...
  19. 2

    Unit Vectors for Tangent Line at (\pi/6, 1)

    Homework Statement Find the unit vectors that are parallel to the tangent line to the curve y=2sinx at the point (\pi/6, 1). Thereafter, find the unit vectors that are perpendicular to the tangent line. Homework Equations The Attempt at a Solution I took the derivative of y=2sinx and...
  20. F

    Easy tangent line problem but I don't know how to approach it

    Let f be the funtion given by f(x) = 4x^2 - x^3 , let L be the line y = 18 - 3x, where L is tangent to the graph of f. Show that L is the tangent to the graph of y= f(x) at the point x = 3. I'm equaling both graphs like this: 4x^2 - x^3 = 18 - 3x and then I isolate everything...
  21. A

    Finding a Tangent Line to a Curve: Exploring Slopes

    A tangent to a curve is a line that touches the curve but at what specific point where there is a slope to the curve. Equations like y = X^2 have many slopes because the curve is shaped differently at different points. We can choose 2 points on the graph and find the slope but it will...
  22. C

    Answer Check - Find an equation of the tangent line

    Homework Statement Find an equation of the tangent line to the curve y = 5x3 at the point (-3,-135). Enter your equation in y = form. Homework Equations The Attempt at a Solution Taking the derivative of the equation I get y = 15x2, following that I plug in the x value of...
  23. H

    Help finding equation of the tangent line to the graph

    Homework Statement Find the equation of the tangent line to the graph of x^2 - xy + y^2 = 19 (where y=y(x)) at (3,-2). Homework Equations The Attempt at a Solution So, this is what I did: d/dx(x^2-xy+y^2) = (19)d/dx 2x*dx/dx-dy/dx+dy/dx+2y(dy/dx)=0 2x+2y(dy/dx)=0 And I...
  24. T

    Find the equation of tangent line

    Homework Statement Find equation of the tangent line at t=0 x=2sint y=tant The Attempt at a Solution Really don't know where to start, can someone give me the hint, don't solve it, i want to try it, just need a hint
  25. T

    Finding a value of theta for which a tangent line is horizontal

    Homework Statement Find the smallest positive value for `theta` for which the tangent line to the curve `r = 6 e^(0.4 theta)` is horizontal The Attempt at a Solution I tried to use the (r'sin(theta)+rcos(theta))/(r'cos(theta) - rsin(theta)) formula to get the tangent line, which I got...
  26. N

    How Do You Find Points with Horizontal Tangents on f(x) = 2sinx + (sinx)^2?

    Homework Statement Find all points on the graph of the function at which the tangent line is horizontal. f(x) = 2sinx + (sinx)^2 Homework Equations Hi guys I have an issue. I do not know how to approach this problem. I know the chain rule but I still do not know how to solve the...
  27. P

    What is the Equation of the Tangent Line on an Ellipse?

    Homework Statement The equation of tangent is given t:2x+3y-2=0 and the equation of elipse E:x^2+4y^2=K Find "a" and "b" and the coordinates of touching point D. Homework Equations equation of elipse: b^2x^2+a^2y^2=a^2b^2 equation for touching: a^2k^2+b^2=n^2 equation for K (if...
  28. C

    For which value of x horizontal Tangent Line

    For which value of x...horizontal Tangent Line Homework Statement For which value of x does f(x) = \frac{k}{ax^{2}+bx+c} have a horizontal tangent line? Homework Equations Quotient Rule? F'(x) = [g(x)a'(x) - a(x)g'(x)]/g(x)^2? The Attempt at a Solution Am I supposed to...
  29. M

    Where tangent line = 0 (parametric)

    Homework Statement At which point is the tanget line to the following curve horizontal? y= a sin^{3}\theta x = acos^{3}\theta Homework Equations The Attempt at a Solution \frac{dy}{dx}=\frac{\frac{dy}{d\theta}}{\frac{dx}{d\theta}} When \frac{dy}{dx} = 0 , this means that that the tanget...
  30. L

    Velocity Vector Versus Tangent Line

    I have encountered a problem in my Calculus homework. I have a position function, r(t)= (t^2)i + (4t)j and in my homework, I am asked to find the tangent to this curve at the point t=3. I did this by finding dy/dx, or 2t/4 @ t=3 is 6/4. However, I am also asked to relate this to the...
  31. B

    Which Points on an Ellipse Have Tangent Lines Passing Through (0,3)?

    Given equation x^2/9 + y^2/4 = 1. Determine the two points on the ellipse having a tangent line passing through the point (0,3). Cant seem to figure this one out? I have found the derivative of the slope which is -4x/9y. I don't know how to use that slope in order to find a tangent line that...
  32. C

    Calculus tangent line problem.

    1. Find the equations of all tangents to the graph f(x) = x^2-4x + 25 that pass through the origin. 2. The relevant equations to my knowledge are the slope formula and f ' (x) 3. First I found the derivative using various rules to be f ' (x) = 2x - 4 after this i used the slope formula and my...
  33. D

    Finding equation to tangent line

    Hello, I'm having trouble understanding an example from my test and I would appreciate your help clarifying how to get from one step to the next. Problem: Find an equation of the tangent line to the hyberola y = 3/x at the point (3,1) Eqation: m = \frac{f(a+h) - f(a)}{h} m =...
  34. S

    OrCad Spice - plotting tangent line of curve

    Hi, I'm having trouble plotting the tangent line on a curve (or the derivative evaluated at a point) in spice. I know how to plot the derivative of the entire curve using the d() function, but I don't know how to evaluate it at a point. Any help is much appreciated!
  35. N

    Tangent line toa curve that minimizes the area of a triangle

    Sorry if the title is a bit vague :/ The Problem: Find the point on the parabola y=1-x^2 at which the tangent line cuts from the first quadrant a triangle with the smallest area. Relevant Equations: y = 1-x^2 ; y' = -2x ; A= 1/2bh I'm basically stuck near square one, I found...
  36. E

    Quick tangent line question (calc final tomorrow)

    1. The problem statement, all variables and given/known i have to find all tangent lines in the equation below that pass though the point (0,0) y=x^{3}+ 6x^{2}+8i took the derivative and got this. y=3x^{2}+12x then i substituted the points x=0 and y=0 into the derivative equation and the...
  37. F

    Finding f'(2): Solving a Tangent Line Problem

    Homework Statement if the tangent line to the graph of y=f(x) at (2.3) has an equation x-y+1=0, then f'(2) =? The Attempt at a Solution We did these problems in one small session at the beginning of the semester, but my notes aren't clear and I am not sure where to begin. Do I just...
  38. E

    Is my equation of the tangent line at (2,-1) correct?

    i would like to know if my answer is correct can someone tell me the results for this: Find the equation of the tangent line to x^3-2x^2y+y^2=17 at (2,-1) ive gotten y'=(3x^2+4xy)/(-2x^2-y) and my line equations is y+1=(-1/4)(x-2) thanks in advance
  39. F

    What is the tangent line to the curve at the given point?

    Homework Statement Find the tangent line to the curve y^2 (y^2 - 4) = x^2 (x^2 -5) at the point (0,-2). Homework Equations y-y1=m(x-x1) The Attempt at a Solution I d/dx-ed both sides and was left with dy/dx=0 so y=-2 Does that seem right?
  40. P

    Derivative and Tangent Line Equation

    [SOLVED] Derivative and tangent line Homework Statement y = (x)/(x+x^-1) Find an equation of the tanget line to the graph at x=2 Homework Equations The Attempt at a Solution I used the quotient rule and got the derivative to be 0 / (x+x^-1) = y' so then the slope is 0 of the...
  41. P

    How to Find Tangent Lines to Y=x^2 Passing Through (2,3) [SOLVED] Tangent Line

    [SOLVED] Tangent Line Homework Statement Find all tangent lines that are tangent to Y=x^2 and go through the point (2,3) Homework Equations The Attempt at a Solution At first I thought I knew how to do this problem, I found the derivative of the equation got: y' = 2x ; then...
  42. C

    R3 Tangent Line at a Point (1,1,1) for x=t^4, y=t^4, z=t^3

    Homework Statement Find parametric equations for the tangent line to the curve x= t^4, y= t^4, z=t^3 at the point (1,1,1) Homework Equations The Attempt at a Solution I understand everything about solving this problem with the exception of how to find what t =? to plug in. ie...
  43. S

    Solving for f'(2) & f(2): A Tangent Line Challenge

    Homework Statement suppose y=2x-3 is an en equation of the tangent line to the graph of y=f(x) at the point where x=2. find the value of f'(2) and f(2). Homework Equations I know how to get the tangent line, but this wording throws me off. a little help at how to solve f(2) and f'(2)...
  44. K

    Equation of the tangent line to the curve

    Homework Statement Find an equation of the tangent line to the curve: 7*x*e^(x)+8 at (0,8) Homework Equations Derivative I guess? The Attempt at a Solution I know you have to take the derivative of the equation given which I think is 7*x*e^(x) + 7*e^(x) Then you plug it...
  45. C

    Finding the equation for the tangent line.

    Homework Statement find the equation for the tangent line. 1. (e^x)(cos x) where x=0Homework Equations plugged 0 into the equation, (e^0)(cos 0) and got 1 for the y-coordinate. so I got the points(0,1). For the slope, I derived the equation into -(e^x)(sin x). then i plugged 0 in and got 0 for...
  46. S

    Finding Parametric Equations for Tangent Line of Surface Intersection

    Homework Statement 5. Find parametric equations for the tangent line to the curve of intersection of the surfaces z^2 = x^2 + y^2 and x^2 + 2y^2 + z^2 = 66 at the point (3, 4, 5). The Attempt at a Solution f(x,y,z) = x^2 + y^2 - z^2 g(x,y,z) = x^2 + 2y^2 + z^2 Partial derivz...
  47. S

    Find the equation of a tangent line to y=f(x)

    Homework Statement Find the equation of the tangent line to the curve at the given point. y = \sqrt{2x+1} , (4, 3)Homework Equations a = 4 M =\lim_{x \to a} \frac{f(x) - f(a)}{x-a} or Mpq = \lim_{h \to 0} \frac{f(a+h) - f(a)}{h} The Attempt at a Solution M =\lim_{x \to 4} \frac{f(x) -...
  48. A

    Solving Tangent Line Problem: 2y^3 + (6x^2)y - 12x^2 + 6y = 1

    Hi, I was wondering if anyone could help. Consider the curve given by: 2y^3 + (6x^2)y - 12x^2 + 6y = 1 I solved the derivative which came out to be (4x-2xy)/(x^2 + y^2 + 1 1. Write an equation of each horizontal tangent line to the curve. 2. The line through the origin with slope -1...
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