# 36 Lecture

## Length of Plane Curves

A plane curve is a two-dimensional curve that can be described by a function of two variables, usually denoted by x and y.

## Important Mcq's Midterm & Finalterm Prepration Past papers included

Which formula is used to calculate the length of a curve?

a) The area formula

b) The perimeter formula

c) The arc length formula

d) The tangent line formula

Solution: c) The arc length formula is used to calculate the length of a curve.

What is the arc length formula?

a) L = ?[a,b] ?(1 + (dy/dx)²) dx

b) L = ?[a,b] (dy/dx) dx

c) L = ?[a,b] ?(1 + (dx/dy)²) dy

d) L = ?[a,b] (dx/dy) dy

Solution: a) The arc length formula is L = ?[a,b] ?(1 + (dy/dx)²) dx.

Which of the following is a smooth curve?

a) A piecewise linear curve

b) A parabolic curve

c) A circle

d) A fractal curve

Solution: b) A parabolic curve is a smooth curve, as it has a continuous and differentiable derivative.

How do we find the length of a circle?

a) L = ?r²

b) L = 2?r

c) L = ?d

d) L = 2?d

Solution: b) The length of a circle is given by the formula L = 2?r.

How do we find the length of a straight line segment?

a) L = x? - x?

b) L = y? - y?

c) L = ?((x? - x?)² + (y? - y?)²)

d) L = (x? - x?) + (y? - y?)

Solution: c) The length of a straight line segment is given by the distance formula L = ?((x? - x?)² + (y? - y?)²).

Can we use the arc length formula for non-smooth curves?

a) Yes

b) No

Solution: a) Yes, we can use the arc length formula for non-smooth curves by dividing the curve into small sections and approximating its length using the formula for each section.

What is the length of the x-axis?

a) 0

b) 1

c) -1

d) ?

Solution: a) The length of the x-axis is 0, as it is a straight line with no width.

What is the length of the unit circle?

a) ?

b) 2?

c) 3?

d) 4?

Solution: b) The length of the unit circle is 2?, as it has a radius of 1.

How do we find the length of an ellipse?

a) Using a simple formula

b) Using numerical methods

c) Using the arc length formula

d) Using the Pythagorean theorem

Solution: b) The length of an ellipse cannot be found using a simple formula, but it can be approximated using numerical methods.

Can we use the Pythagorean theorem to find the length of a curve?

a) Yes

b) No

Solution: b) No, the Pythagorean theorem cannot be used to find the length of a curve, as it only applies to right triangles.

## Subjective Short Notes Midterm & Finalterm Prepration Past papers included

What is a plane curve?

A plane curve is a two-dimensional curve that can be described by a function of two variables, usually denoted by x and y.

What is the length of a plane curve?

The length of a plane curve is the distance between its endpoints.

How do we calculate the length of a curve?

To calculate the length of a curve, we use the arc length formula, which involves integrating the square root of the sum of the squares of the derivatives of the curve.

What is arc length?

Arc length is the length of a small section of a curve, defined as the distance between two points on the curve that are very close together.

What is the formula for arc length?

The formula for arc length is L = ?[a,b] ?(1 + (dy/dx)²) dx, where dy/dx is the derivative of y with respect to x, and the integral is taken over the interval [a,b].

What is the difference between a smooth curve and a non-smooth curve?

A smooth curve is a curve that has a continuous and differentiable derivative, while a non-smooth curve is a curve that does not have a continuous and differentiable derivative.

Can we use the arc length formula for non-smooth curves?

For non-smooth curves, we can divide the curve into small sections and approximate its length using the arc length formula for each section.

How do we find the length of a circle?

The length of a circle is called its circumference, which is given by the formula C = 2?r, where r is the radius of the circle.

How do we find the length of an ellipse?

The length of an ellipse is not given by a simple formula, but it can be approximated using numerical methods.

Can we use numerical methods to approximate the length of any curve?

Yes, numerical methods such as Simpson's rule or the trapezoidal rule can be used to approximate the length of any curve, even if the arc length formula is difficult or impossible to solve analytically.

### Length of Plane Curves

Calculus and Analytical Geometry is a branch of mathematics that studies the relationships between algebraic and geometric objects, using the tools of calculus to analyze and understand their behavior. One of the fundamental concepts in this field is the length of plane curves, which is the subject of this article. A plane curve is a two-dimensional curve that can be described by a function of two variables, usually denoted by x and y. Examples of plane curves include lines, circles, ellipses, parabolas, and hyperbolas. In calculus, we are interested in finding the length of a curve, which is the distance between its endpoints. To find the length of a plane curve, we first need to understand the concept of arc length. Arc length is the length of a small section of a curve, defined as the distance between two points on the curve that are very close together. To calculate the arc length of a curve, we use a process called integration. Suppose we have a curve described by the equation y=f(x) between two points a and b. To find the arc length of this curve, we divide it into small sections of length ?s, as shown in the diagram below. [insert diagram of curve divided into small sections] The arc length of each section can be approximated by the Pythagorean theorem: ?s = ?(?x² + ?y²) where ?x and ?y are the changes in x and y between two neighboring points on the curve. To find the total arc length of the curve, we sum up the lengths of all the small sections: L = ? ?s As we make the sections smaller and smaller, this sum becomes an integral: L = ?[a,b] ?(1 + (dy/dx)²) dx where dy/dx is the derivative of y with respect to x, and the integral is taken over the interval [a,b]. This formula is known as the arc length formula, and it allows us to calculate the length of any smooth curve. However, for curves that are not smooth, the formula may not apply. In these cases, we can divide the curve into small sections and approximate its length using the arc length formula for each section. Let's consider some examples to illustrate the use of the arc length formula. Suppose we want to find the length of the curve y=x² between x=0 and x=1. We can use the formula: L = ?[0,1] ?(1 + 4x²) dx Solving this integral, we get: L = (1/2)?(17) + (1/4)sinh?¹(2) which is approximately 1.478. As another example, let's find the length of the curve y=ln(x) between x=1 and x=e. We have: L = ?[1,e] ?(1 + (1/x)²) dx Solving this integral, we get: L = e - 1 + ln(e + ?(e² - 1)) which is approximately 2.388. In some cases, the arc length formula may be difficult or impossible to solve analytically. In these cases, we can use numerical methods, such as Simpson's rule or the trapezoidal rule, to approximate the integral and find an approximate value for the length of the curve. In conclusion, the length of plane curves is an important concept in calculus and analytical geometry. To find the length of a curve, we use the arc length formula, which involves integrating the square root of the sum of the squares of the derivatives of the curve. This formula allows us to calculate the length