Get the most out of your questions with IDNLearn.com's extensive resources. Discover reliable answers to your questions with our extensive database of expert knowledge.

Find an equation of the tangent to the curve at the given point by two methods:
(a) without eliminating the parameter and
(b) by first eliminating the parameter.
x = 1 + ln t, y = t2 + 2; (1, 3)


Sagot :

Answer:

1) y = 2x + 1

2) y = 2x + 1

Step-by-step explanation:

The parametric equation given is;

x = 1 + ln t and y = t² + 2 at (1, 3)

1) without eliminating the parameter;

Using, x = 1 + ln t ;

dx/dt = 1/t

Using y = t² + 2;

dy/dt = 2t

Slope which is dy/dx is gotten from;

dy/dx = (dy/dt)/(dx/dt)

dy/dx = 2t/(1/t)

dy/dx = 2t²

For x = 1 + In t, at x = 1, we have;

1 = 1 + In t

In t = 0

t = 1

For y = t² + 2, at y = 3, we have;

3 = t² + 2

t² = 3 - 2

t² = 1

t = ±1

Since t = ±1, then;

dy/dx = 2(±1)²

dy/dx = 2

Equation of the tangent is;

y - 3 = 2(x - 1)

y - 3 = 2x - 2

y = 2x - 2 + 3

y = 2x + 1

2) By eliminating the parameter

x = 1 + In t

Let's make t the subject of the equation.

In t = x - 1

t = e^(x - 1)

Let's put e^(x - 1) for t in y = t² + 2

Thus;

y = e^(x - 1)² + 2

y = e^(2(x - 1)) + 2

Thus, parameter has been eliminated

Equation of the tangent is gotten from;

y - y1 = m(x - x1)

m is gradient = dy/dx = 2e^(2(x - 1))

at (1, 3), we have x = 1. Thus;

m = 2e^(2(1 - 1))

m = 2e^0

m = 2

Thus, equation of tangent at (1,3) is;

y - 3 = 2(x - 1)

y - 3 = 2x - 2

y = 2x - 2 + 3

y = 2x + 1