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The area of the region bounded by y = f(x), the ordinates x = a, x =b, and the X-axis is âˆ«_{a}^{b} f(x) dx, where a â‰¤ x â‰¤ b.

Let x be any point in the closed interval [a, b] such that f(x) > 0 âˆ€ x âˆˆ [a,b].

âˆ«_{a}^{r} f(x) dx represents the area of the shaded region.

The area of the shaded region depends on the value of x.

Therefore, the area of the shaded region is a function of x.

We represent the function of x as A(x).

Area function , A(x) = âˆ«_{a}^{x} f(x) dx

**First fundamental theorem on integral calculus:**

1) If f is a continuous function defined on

Closed interval [a, b] and A(x) be the area function, then A'(x) = f(x), âˆ€ x âˆˆ [a,b].

**Second fundamental theorem on integral calculus:**

2) Let f be a function defined on closed interval [a, b] and let g be an anti-derivate of function f, then:

âˆ«_{a}^{b} f(x) dx = (Value of the anti- derivative of g of f at the upper limit) - (value of the anti - derivative g o f at lower limit)

Mathematically, it can be denoted as

âˆ«_{a}^{b} f(x) dx = [g(x)]_{a}^{b} = g(b) - g(a)

This theorem is applicable only when f is well defined in the closed interval [a, b].

__Steps to calculate__** âˆ« _{a}^{b} f(x) dx**

Step: 1) Find âˆ« f(x) dx

Let g(x) = âˆ« f(x) dx.

Step: 2) âˆ«_{a}^{b} f(x) dx = [g(x) + C]_{a}^{b}

= [g(b) + C] - [g(a) + C]

= g(b) - g(a)

The area of the region bounded by y = f(x), the ordinates x = a, x =b, and the X-axis is âˆ«_{a}^{b} f(x) dx, where a â‰¤ x â‰¤ b.

Let x be any point in the closed interval [a, b] such that f(x) > 0 âˆ€ x âˆˆ [a,b].

âˆ«_{a}^{r} f(x) dx represents the area of the shaded region.

The area of the shaded region depends on the value of x.

Therefore, the area of the shaded region is a function of x.

We represent the function of x as A(x).

Area function , A(x) = âˆ«_{a}^{x} f(x) dx

**First fundamental theorem on integral calculus:**

1) If f is a continuous function defined on

Closed interval [a, b] and A(x) be the area function, then A'(x) = f(x), âˆ€ x âˆˆ [a,b].

**Second fundamental theorem on integral calculus:**

2) Let f be a function defined on closed interval [a, b] and let g be an anti-derivate of function f, then:

âˆ«_{a}^{b} f(x) dx = (Value of the anti- derivative of g of f at the upper limit) - (value of the anti - derivative g o f at lower limit)

Mathematically, it can be denoted as

âˆ«_{a}^{b} f(x) dx = [g(x)]_{a}^{b} = g(b) - g(a)

This theorem is applicable only when f is well defined in the closed interval [a, b].

__Steps to calculate__** âˆ« _{a}^{b} f(x) dx**

Step: 1) Find âˆ« f(x) dx

Let g(x) = âˆ« f(x) dx.

Step: 2) âˆ«_{a}^{b} f(x) dx = [g(x) + C]_{a}^{b}

= [g(b) + C] - [g(a) + C]

= g(b) - g(a)