x - 2 / | | 1 | -------- dx | sin(2*x) | / x - 4
Integral(1/sin(2*x), (x, x/4, x/2))
/ | | 1 | -------- dx | sin(2*x) | /
1 -------- sin(2*x)
sin(2*x)
1 sin(2*x) -------- = --------- sin(2*x) 2 sin (2*x)
sin(a)^2 + cos(a)^2 = 1
2 2 sin (2*x) = 1 - cos (2*x)
sin(2*x) sin(2*x) --------- = ------------- 2 2 sin (2*x) 1 - cos (2*x)
u = cos(2*x)
/ | | sin(2*x) | ------------- dx | 2 = | 1 - cos (2*x) | /
/ | | sin(2*x) | ------------- dx | 2 = | 1 - cos (2*x) | /
/ | | -1 | ---------- du | / 2\ | 2*\1 - u / | /
-1 -1 / 1 1 \ ---------- = ---*|----- + -----| / 2\ 2*2 \1 - u 1 + u/ 2*\1 - u /
/ / | | | 1 | 1 | ----- du | ----- du / | 1 + u | 1 - u | | | | -1 / / = | ---------- du = - ----------- - ----------- | / 2\ 4 4 | 2*\1 - u / | /
= -log(1 + u)/4 + log(-1 + u)/4
u = cos(2*x)
/ | | 1 log(1 + cos(2*x)) log(-1 + cos(2*x)) | -------- dx = - ----------------- + ------------------ + C0 | sin(2*x) 4 4 | /
/ | | 1 log(1 + cos(2*x)) log(-1 + cos(2*x)) | -------- dx = C - ----------------- + ------------------ | sin(2*x) 4 4 | /
/ /x\\ / /x\\ log|-1 + cos|-|| log|1 + cos|-|| log(1 + cos(x)) \ \2// \ \2// log(-1 + cos(x)) - --------------- - ---------------- + --------------- + ---------------- 4 4 4 4
=
/ /x\\ / /x\\ log|-1 + cos|-|| log|1 + cos|-|| log(1 + cos(x)) \ \2// \ \2// log(-1 + cos(x)) - --------------- - ---------------- + --------------- + ---------------- 4 4 4 4
-log(1 + cos(x))/4 - log(-1 + cos(x/2))/4 + log(1 + cos(x/2))/4 + log(-1 + cos(x))/4
Estos ejemplos se pueden aplicar para introducción de los límites de integración inferior y superior.