USING DERIVATIVES FIND EQUATION OF TANGENT AND NORMAL

Problem 1 :

Find the slope of the tangent to the curves at the respective given points.

(i) y = x4 + 2x2 − x at x = 1

(ii)  x  =  a cos3t, y = b sin3t at t  =  π/2

Solution

Problem 2 :

Find the point on the curve y = x2 − 5x + 4 at which the tangent is parallel to the line 3x + y = 7 .

Solution

Problem 3 :

Find the points on the curve y = x3 − 6x2 + x + 3 where the normal is parallel to the line x + y  =  1729.

Solution

Problem 4 :

Find the points on the curve y2 - 4xy  =  x2+ 5 for which the tangent is horizontal.

Solution

Problem 5 :

The normal at the point (1, 1) on the curve 2y + x2 = 3 is

(a) x + y = 0     (b) x - y = 0    (c) x + y + 1 = 0  (d) x - y = 0

Solution

Problem 6 :

Find the points on the curve

x2/9 + y2/16 = 1

at which the tangents are parallel to Y-axis

Solution

Answer Key

1)  i)  slope of the tangent at x  =  1  is 7.

ii)  slope of the tangent at x  =  π/2 is 

2)  the required point is (1, 0).

3)   the required points are (0, 3) and (4, -25).

4)   the required points are (-2, 1) and (2, -1).

5) x - y = 0

6)  the points at which the tangents are parallel to the y-axis are (3,0) and (−3,0).

Problem 1 :

Find the tangent and normal to the following curves at the given points on the curve.

(i)  y  =  x2 - x4 at (1, 0)

(ii)  y  =  x+ 2ex at (0, 2)

(iii)  y  =  x sin x at (π/2, π/2)

(iv)  x  =  cost, y  =  2 sin2t at t  =  π/3

Solution

Problem 2 :

Find the tangent and normal to the curve x3 + y3 = 2xy at (1, 1).

Solution

Problem 3 :

Consider the curve defined by 2y3 + 6x2 y - 12x2 + 6y = 1

i) Find dy/dx

ii)  Write an equation of each horizontal tangent line to the curve.

iii) The line through the origin with slope -1 is tangent to the curve at point P. Find the x and y coordinate of P.

Solution

Answer Key

1)  i)  equation of normal is x - 2y - 1 = 0.

ii)  equation of tangent is 2x - y + 2 = 0 and equation of normal is x + 2y - 4 = 0.

iii)  equation of tangent x - y = 0

equation of normal x + y - π = 0

iv) Equation of tangent is 4x + 2y - 5 = 0

equation of normal is 2x - 4y + 5 = 0

2)  i)  equation of tangent is x + y = 2

equation of normal is x - y = 0

3)  i)  dy/dx = (- 2xy + 4x) / (y2 + x2 + 1)

ii)  There are no points on the curve where y = 2.

iii)  the required point is (-1/2, 1/2).

Problem 1 :

Find the equations of the tangents to the curve

y  =  1+x3

for which the tangent is orthogonal with the line

x+12y  =  12

Solution

Problem 2 :

Find the equations of the tangents to the curve

y  =  (x+1)/(x-1)

which are parallel to the line x+2y  =  6.

Solution

Problem 3 :

Find the equation of tangent and normal to the curve given by

x  =  7 cos t and y  =  2 sin t for all t

at any point on the curve.              Solution

Problem 4 :

Find the angle between the rectangular hyperbola xy = 2 and the parabola x2 + 4y = 0 .

Solution

Problem 5 :

Show that the two curves x2 − y2 = r2 and xy = c2 where c, r are constants, cut orthogonally 

Solution

Answer Key

1)  Equation of tangent is 12x - y - 15 = 0

Equation of normal is 12x - y + 17 = 0

2)  Equation of tangent is x + 2y - 7 = 0

Equation of normal is x + 2y + 1 = 0

3)  Equation of tangent is (2cost) x + (7sint)y  =  14

Equation of normal is (7sint)x - (2cost)y - 45sint cost  =  0

4) Equation of tangent is 12x + 36y = 227

5)  Equation of tangent is x + 14y - 114 = 0

Equation of normal is x + 14y + 86 = 0

Example 1 :

Find the points on curve

x2-y2  =  2

at which the slope of the tangent is 2.

Solution

Example 2 :

Find at what points on a circle

x2+y2  =  13

the slope of the tangent is -2/3.

Solution

Example 3 :

For the curve y = 4x3 -2x5, find all the points at which the tangent passes through the origin.

Solution

Example 4 :

The curve

y = ax+ bx+ cx + 5

touches the x-axis at the point (-2, 0) and Cuts the y-axis at a point where the slope is 3. Find a, b, c

Solution

Example 5 :

The point on the curve y = x3 – 11x + 5 at which the tangent is y = x –11 is

Solution

Example 6 :

The line y = x + 1 is a tangent to the curve y2 = 4x at the point

(a) (1, 2)     (b) (2, 1)    (c) (1, – 2)   (d) (–1 ,2)

Solution

Answer Key

1)  the required points are

(2√(2/3), √(2/3)) and (-2√(2/3), - √(2/3))

2)  the required points are (2, 3) (-2, -3).

3)   points are (0, 0) (-1, -2) and (1, 2).

4) the values of a = -1/2, b = -3/4 and c = 3.

5) the required points are (-2, 19) and (2, 9).

6)  (1, 2)

Kindly mail your feedback to v4formath@gmail.com

We always appreciate your feedback.

©All rights reserved. onlinemath4all.com

Recent Articles

  1. Digital SAT Math Problems and Solutions (Part - 167)

    May 22, 25 09:59 AM

    digitalsatmath211.png
    Digital SAT Math Problems and Solutions (Part - 167)

    Read More

  2. AP Calculus AB Problems with Solutions (Part - 23)

    May 21, 25 01:19 PM

    apcalculusab22.png
    AP Calculus AB Problems with Solutions (Part - 23)

    Read More

  3. Digital SAT Math Problems and Solutions (Part - 166)

    May 21, 25 05:33 AM

    digitalsatmath210.png
    Digital SAT Math Problems and Solutions (Part - 166)

    Read More