해법
∫sin4(21x)cos4(21x)dx
해법
2(−41sin3(2x)cos(2x)+163(x−sin(x))−2563(5(3(x−sin(x))−4sin3(2x)cos(2x))−16sin5(2x)cos(2x))−81sin7(2x)cos(2x))+C
솔루션 단계
∫sin4(21x)cos4(21x)dx
sin4(21x)cos4(21x)단순화하세요:sin4(2x)cos4(2x)
=∫sin4(2x)cos4(2x)dx
대체 적용:∫sin4(u)cos4(u)⋅2du
=∫sin4(u)cos4(u)⋅2du
정수를 빼라: ∫a⋅f(x)dx=a⋅∫f(x)dx=2⋅∫sin4(u)cos4(u)du
삼각성을 사용하여 다시 쓰기
=2⋅∫sin4(u)(1−sin2(u))2du
sin4(u)(1−sin2(u))2확대한다:sin4(u)−2sin6(u)+sin8(u)
=2⋅∫sin4(u)−2sin6(u)+sin8(u)du
합계 규칙 적용: ∫f(x)±g(x)dx=∫f(x)dx±∫g(x)dx=2(∫sin4(u)du−∫2sin6(u)du+∫sin8(u)du)
∫sin4(u)du=−41sin3(u)cos(u)+83(u−21sin(2u))
∫2sin6(u)du=2(−6cos(u)sin5(u)+65(−41sin3(u)cos(u)+83(u−21sin(2u))))
∫sin8(u)du=−8cos(u)sin7(u)+87(−6cos(u)sin5(u)+65(−41sin3(u)cos(u)+83(u−21sin(2u))))
=2(−41sin3(u)cos(u)+83(u−21sin(2u))−2(−6cos(u)sin5(u)+65(−41sin3(u)cos(u)+83(u−21sin(2u))))−8cos(u)sin7(u)+87(−6cos(u)sin5(u)+65(−41sin3(u)cos(u)+83(u−21sin(2u)))))
뒤로 대체 u=2x=2(−41sin3(2x)cos(2x)+83(2x−21sin(2⋅2x))−2(−6cos(2x)sin5(2x)+65(−41sin3(2x)cos(2x)+83(2x−21sin(2⋅2x))))−8cos(2x)sin7(2x)+87(−6cos(2x)sin5(2x)+65(−41sin3(2x)cos(2x)+83(2x−21sin(2⋅2x)))))
2(−41sin3(2x)cos(2x)+83(2x−21sin(2⋅2x))−2(−6cos(2x)sin5(2x)+65(−41sin3(2x)cos(2x)+83(2x−21sin(2⋅2x))))−8cos(2x)sin7(2x)+87(−6cos(2x)sin5(2x)+65(−41sin3(2x)cos(2x)+83(2x−21sin(2⋅2x)))))간소화하다 :2(−41sin3(2x)cos(2x)+163(x−sin(x))−2563(5(3(x−sin(x))−4sin3(2x)cos(2x))−16sin5(2x)cos(2x))−81sin7(2x)cos(2x))
=2(−41sin3(2x)cos(2x)+163(x−sin(x))−2563(5(3(x−sin(x))−4sin3(2x)cos(2x))−16sin5(2x)cos(2x))−81sin7(2x)cos(2x))
솔루션에 상수 추가=2(−41sin3(2x)cos(2x)+163(x−sin(x))−2563(5(3(x−sin(x))−4sin3(2x)cos(2x))−16sin5(2x)cos(2x))−81sin7(2x)cos(2x))+C