해법
sin(x)cos(2x)=21(1+sin(x))
해법
x=−0.86437…+2πn,x=π+0.86437…+2πn
+1
도
x=−49.52505…∘+360∘n,x=229.52505…∘+360∘n솔루션 단계
sin(x)cos(2x)=21(1+sin(x))
빼다 21(1+sin(x)) 양쪽에서sin(x)cos(2x)−21(1+sin(x))=0
sin(x)cos(2x)−21(1+sin(x))단순화하세요:22sin(x)cos(2x)−1−sin(x)
sin(x)cos(2x)−21(1+sin(x))
21(1+sin(x))=21+sin(x)
21(1+sin(x))
다중 분수: a⋅cb=ca⋅b=21⋅(1+sin(x))
1⋅(1+sin(x))=1+sin(x)
1⋅(1+sin(x))
곱하다: 1⋅(1+sin(x))=(1+sin(x))=(1+sin(x))
괄호 제거: (a)=a=1+sin(x)
=21+sin(x)
=sin(x)cos(2x)−2sin(x)+1
요소를 분수로 변환: sin(x)cos(2x)=2sin(x)cos(2x)2=2sin(x)cos(2x)⋅2−21+sin(x)
분모가 같기 때문에, 분수를 합친다: ca±cb=ca±b=2sin(x)cos(2x)⋅2−(1+sin(x))
sin(x)cos(2x)⋅2−(1+sin(x))확대한다:sin(x)cos(2x)⋅2−1−sin(x)
sin(x)cos(2x)⋅2−(1+sin(x))
=2sin(x)cos(2x)−(1+sin(x))
−(1+sin(x)):−1−sin(x)
−(1+sin(x))
괄호 배포=−(1)−(sin(x))
마이너스 플러스 규칙 적용+(−a)=−a=−1−sin(x)
=sin(x)cos(2x)⋅2−1−sin(x)
=22sin(x)cos(2x)−1−sin(x)
22sin(x)cos(2x)−1−sin(x)=0
g(x)f(x)=0⇒f(x)=02sin(x)cos(2x)−1−sin(x)=0
삼각성을 사용하여 다시 쓰기
−1−sin(x)+2cos(2x)sin(x)
더블 앵글 아이덴티티 사용: cos(2x)=1−2sin2(x)=−1−sin(x)+2(1−2sin2(x))sin(x)
−1−sin(x)+2(1−2sin2(x))sin(x)간소화하다 :−1+sin(x)−4sin3(x)
−1−sin(x)+2(1−2sin2(x))sin(x)
=−1−sin(x)+2sin(x)(1−2sin2(x))
2sin(x)(1−2sin2(x))확대한다:2sin(x)−4sin3(x)
2sin(x)(1−2sin2(x))
분배 법칙 적용: a(b−c)=ab−aca=2sin(x),b=1,c=2sin2(x)=2sin(x)⋅1−2sin(x)⋅2sin2(x)
=2⋅1⋅sin(x)−2⋅2sin2(x)sin(x)
2⋅1⋅sin(x)−2⋅2sin2(x)sin(x)단순화하세요:2sin(x)−4sin3(x)
2⋅1⋅sin(x)−2⋅2sin2(x)sin(x)
2⋅1⋅sin(x)=2sin(x)
2⋅1⋅sin(x)
숫자를 곱하시오: 2⋅1=2=2sin(x)
2⋅2sin2(x)sin(x)=4sin3(x)
2⋅2sin2(x)sin(x)
숫자를 곱하시오: 2⋅2=4=4sin2(x)sin(x)
지수 규칙 적용: ab⋅ac=ab+csin2(x)sin(x)=sin2+1(x)=4sin2+1(x)
숫자 추가: 2+1=3=4sin3(x)
=2sin(x)−4sin3(x)
=2sin(x)−4sin3(x)
=−1−sin(x)+2sin(x)−4sin3(x)
유사 요소 추가: −sin(x)+2sin(x)=sin(x)=−1+sin(x)−4sin3(x)
=−1+sin(x)−4sin3(x)
−1+sin(x)−4sin3(x)=0
대체로 해결
−1+sin(x)−4sin3(x)=0
하게: sin(x)=u−1+u−4u3=0
−1+u−4u3=0:u≈−0.76068…
−1+u−4u3=0
표준 양식으로 작성 anxn+…+a1x+a0=0−4u3+u−1=0
다음을 위한 하나의 솔루션 찾기 −4u3+u−1=0 뉴턴-랩슨을 이용하여:u≈−0.76068…
−4u3+u−1=0
뉴턴-랩슨 근사 정의
f(u)=−4u3+u−1
f′(u)찾다 :−12u2+1
dud(−4u3+u−1)
합계/차이 규칙 적용: (f±g)′=f′±g′=−dud(4u3)+dudu−dud(1)
dud(4u3)=12u2
dud(4u3)
정수를 빼라: (a⋅f)′=a⋅f′=4dud(u3)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=4⋅3u3−1
단순화=12u2
dudu=1
dudu
공통 도함수 적용: dudu=1=1
dud(1)=0
dud(1)
상수의 도함수: dxd(a)=0=0
=−12u2+1−0
단순화=−12u2+1
렛 u0=−1계산하다 un+1 까지 Δun+1<0.000001
u1=−0.81818…:Δu1=0.18181…
f(u0)=−4(−1)3+(−1)−1=2f′(u0)=−12(−1)2+1=−11u1=−0.81818…
Δu1=∣−0.81818…−(−1)∣=0.18181…Δu1=0.18181…
u2=−0.76519…:Δu2=0.05298…
f(u1)=−4(−0.81818…)3+(−0.81818…)−1=0.37265…f′(u1)=−12(−0.81818…)2+1=−7.03305…u2=−0.76519…
Δu2=∣−0.76519…−(−0.81818…)∣=0.05298…Δu2=0.05298…
u3=−0.76072…:Δu3=0.00447…
f(u2)=−4(−0.76519…)3+(−0.76519…)−1=0.02696…f′(u2)=−12(−0.76519…)2+1=−6.02629…u3=−0.76072…
Δu3=∣−0.76072…−(−0.76519…)∣=0.00447…Δu3=0.00447…
u4=−0.76068…:Δu4=0.00003…
f(u3)=−4(−0.76072…)3+(−0.76072…)−1=0.00018…f′(u3)=−12(−0.76072…)2+1=−5.94435…u4=−0.76068…
Δu4=∣−0.76068…−(−0.76072…)∣=0.00003…Δu4=0.00003…
u5=−0.76068…:Δu5=1.46429E−9
f(u4)=−4(−0.76068…)3+(−0.76068…)−1=8.70343E−9f′(u4)=−12(−0.76068…)2+1=−5.94378…u5=−0.76068…
Δu5=∣−0.76068…−(−0.76068…)∣=1.46429E−9Δu5=1.46429E−9
u≈−0.76068…
긴 나눗셈 적용:u+0.76068…−4u3+u−1=−4u2+3.04275…u−1.31459…
−4u2+3.04275…u−1.31459…≈0
다음을 위한 하나의 솔루션 찾기 −4u2+3.04275…u−1.31459…=0 뉴턴-랩슨을 이용하여:솔루션 없음 u∈R
−4u2+3.04275…u−1.31459…=0
뉴턴-랩슨 근사 정의
f(u)=−4u2+3.04275…u−1.31459…
f′(u)찾다 :−8u+3.04275…
dud(−4u2+3.04275…u−1.31459…)
합계/차이 규칙 적용: (f±g)′=f′±g′=−dud(4u2)+dud(3.04275…u)−dud(1.31459…)
dud(4u2)=8u
dud(4u2)
정수를 빼라: (a⋅f)′=a⋅f′=4dud(u2)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=4⋅2u2−1
단순화=8u
dud(3.04275…u)=3.04275…
dud(3.04275…u)
정수를 빼라: (a⋅f)′=a⋅f′=3.04275…dudu
공통 도함수 적용: dudu=1=3.04275…⋅1
단순화=3.04275…
dud(1.31459…)=0
dud(1.31459…)
상수의 도함수: dxd(a)=0=0
=−8u+3.04275…−0
단순화=−8u+3.04275…
렛 u0=0계산하다 un+1 까지 Δun+1<0.000001
u1=0.43204…:Δu1=0.43204…
f(u0)=−4⋅02+3.04275…⋅0−1.31459…=−1.31459…f′(u0)=−8⋅0+3.04275…=3.04275…u1=0.43204…
Δu1=∣0.43204…−0∣=0.43204…Δu1=0.43204…
u2=−1.37331…:Δu2=1.80535…
f(u1)=−4⋅0.43204…2+3.04275…⋅0.43204…−1.31459…=−0.74663…f′(u1)=−8⋅0.43204…+3.04275…=−0.41356…u2=−1.37331…
Δu2=∣−1.37331…−0.43204…∣=1.80535…Δu2=1.80535…
u3=−0.44402…:Δu3=0.92928…
f(u2)=−4(−1.37331…)2+3.04275…(−1.37331…)−1.31459…=−13.03728…f′(u2)=−8(−1.37331…)+3.04275…=14.02930…u3=−0.44402…
Δu3=∣−0.44402…−(−1.37331…)∣=0.92928…Δu3=0.92928…
u4=0.07974…:Δu4=0.52377…
f(u3)=−4(−0.44402…)2+3.04275…(−0.44402…)−1.31459…=−3.45431…f′(u3)=−8(−0.44402…)+3.04275…=6.59499…u4=0.07974…
Δu4=∣0.07974…−(−0.44402…)∣=0.52377…Δu4=0.52377…
u5=0.53608…:Δu5=0.45633…
f(u4)=−4⋅0.07974…2+3.04275…⋅0.07974…−1.31459…=−1.09737…f′(u4)=−8⋅0.07974…+3.04275…=2.40476…u5=0.53608…
Δu5=∣0.53608…−0.07974…∣=0.45633…Δu5=0.45633…
u6=−0.13247…:Δu6=0.66855…
f(u5)=−4⋅0.53608…2+3.04275…⋅0.53608…−1.31459…=−0.83296…f′(u5)=−8⋅0.53608…+3.04275…=−1.24592…u6=−0.13247…
Δu6=∣−0.13247…−0.53608…∣=0.66855…Δu6=0.66855…
u7=0.30332…:Δu7=0.43579…
f(u6)=−4(−0.13247…)2+3.04275…(−0.13247…)−1.31459…=−1.78786…f′(u6)=−8(−0.13247…)+3.04275…=4.10252…u7=0.30332…
Δu7=∣0.30332…−(−0.13247…)∣=0.43579…Δu7=0.43579…
u8=1.53626…:Δu8=1.23293…
f(u7)=−4⋅0.30332…2+3.04275…⋅0.30332…−1.31459…=−0.75967…f′(u7)=−8⋅0.30332…+3.04275…=0.61615…u8=1.53626…
Δu8=∣1.53626…−0.30332…∣=1.23293…Δu8=1.23293…
u9=0.87871…:Δu9=0.65754…
f(u8)=−4⋅1.53626…2+3.04275…⋅1.53626…−1.31459…=−6.08050…f′(u8)=−8⋅1.53626…+3.04275…=−9.24732…u9=0.87871…
Δu9=∣0.87871…−1.53626…∣=0.65754…Δu9=0.65754…
u10=0.44494…:Δu10=0.43377…
f(u9)=−4⋅0.87871…2+3.04275…⋅0.87871…−1.31459…=−1.72944…f′(u9)=−8⋅0.87871…+3.04275…=−3.98698…u10=0.44494…
Δu10=∣0.44494…−0.87871…∣=0.43377…Δu10=0.43377…
u11=−1.01142…:Δu11=1.45637…
f(u10)=−4⋅0.44494…2+3.04275…⋅0.44494…−1.31459…=−0.75263…f′(u10)=−8⋅0.44494…+3.04275…=−0.51679…u11=−1.01142…
Δu11=∣−1.01142…−0.44494…∣=1.45637…Δu11=1.45637…
해결 방법을 찾을 수 없습니다
해결책은u≈−0.76068…
뒤로 대체 u=sin(x)sin(x)≈−0.76068…
sin(x)≈−0.76068…
sin(x)=−0.76068…:x=arcsin(−0.76068…)+2πn,x=π+arcsin(0.76068…)+2πn
sin(x)=−0.76068…
트리거 역속성 적용
sin(x)=−0.76068…
일반 솔루션 sin(x)=−0.76068…sin(x)=−a⇒x=arcsin(−a)+2πn,x=π+arcsin(a)+2πnx=arcsin(−0.76068…)+2πn,x=π+arcsin(0.76068…)+2πn
x=arcsin(−0.76068…)+2πn,x=π+arcsin(0.76068…)+2πn
모든 솔루션 결합x=arcsin(−0.76068…)+2πn,x=π+arcsin(0.76068…)+2πn
해를 10진수 형식으로 표시x=−0.86437…+2πn,x=π+0.86437…+2πn