The following formula for the sum of the cubes of the first n integers is proved. Use it to evaluate the area under the curve y = x³ from 0 to 1 as a limit,
1³ + 2³ + 3³ +...+ n³ = [n(n+1)/2]².

Respuesta :

Answer:

Therefore, area under the curve is [tex]\frac{1}{4}[/tex]

Step-by-step explanation:

We have to find the area under curve y = x³ from 0 to 1 as limit.

Since Area 'A' = [tex]\lim_{n \to \infty} \sum_{i=1}^{n}f(x_{i})\triangle x[/tex]

The given function is f(x) = x³

Since [tex]x_{i}=a+\triangle x.i[/tex]

Here a = 0 and [tex]\triangle x=\frac{1-0}{n}=\frac{1}{n}[/tex]

[tex]f(x_{i})=(\frac{i}{n})^{3}[/tex]

Now A = [tex]\lim_{n \to \infty} \sum_{i=1}^{n}f(x_{i})\triangle x= \lim_{n \to \infty}\sum_{i=1}^{n}(\frac{i}{n})^{3}(\frac{1}{n})[/tex]

[tex]= \lim_{n \to \infty}\frac{1}{n^{4}}\sum_{i=1}^{n}i^{3}[/tex]

[tex]= \lim_{n \to \infty}\frac{1}{n^{4}}( \frac{n(n+1)}{2})^{2}[/tex]    Since 1³ + 2³ + 3³..............n³ = [tex][\frac{n(n+1)}{2}]^{2}[/tex]

[tex]= \lim_{n \to \infty}\frac{n^{2}(n+1)^{2}}{4n^{4}}[/tex]

[tex]= \lim_{n \to \infty}\frac{1}{4}(1+\frac{1}{n})^{2}[/tex]

[tex]=\frac{1}{4}(1+0)[/tex]

[tex]=\frac{1}{4}[/tex]

Therefore, area under the curve is [tex]\frac{1}{4}[/tex]