Compute the integral (a) int sin (pi x) dx by letting u = pi x. (b) int e^(x/2) dx by letting u = x/2. Show that you got the correct answer by differentiating the computed function.

Respuesta :

Answer:

(a) [tex]\int sin(\pi x) dx[/tex][tex]=-\frac {cos \pi x}{\pi}+c[/tex]

(b)[tex]\int e^\frac{x}{2} dx[/tex] [tex]=2e^\frac{x}{2}+c[/tex]

Step-by-step explanation:

(a)

[tex]\int sin(\pi x) dx[/tex]

Let u = π x

differentiating with respect to x

du = π dx

[tex]\Rightarrow dx=\frac{du}{\pi}[/tex]

Putting the value of x and dx

[tex]=\int sin u \frac{du}{\pi}[/tex]

[tex]=\frac{-cos u}{\pi}+c[/tex]    [ c is an arbitrary constant]

Now putting the value of u

[tex]=-\frac {cos \pi x}{\pi}+c[/tex]  

(b)

[tex]\int e^\frac{x}{2} dx[/tex]

Let [tex]u=\frac{x}{2}[/tex]

differentiating with respect to x

[tex]du= \frac{1}{2} dx[/tex]

2du = dx

Putting the value of x and dx

=[tex]\int e^u.2.du[/tex]

=[tex]2e^u +c[/tex]

Now putting the value of u

[tex]=2e^\frac{x}{2}+c[/tex]       [ c is an arbitrary constant]