해법
2cos(x)+4cos(4x)=0
해법
x=2.87471…+2πn,x=−2.87471…+2πn,x=0.50586…+2πn,x=2π−0.50586…+2πn,x=1.92046…+2πn,x=−1.92046…+2πn,x=1.12361…+2πn,x=2π−1.12361…+2πn
+1
도
x=164.70891…∘+360∘n,x=−164.70891…∘+360∘n,x=28.98415…∘+360∘n,x=331.01584…∘+360∘n,x=110.03427…∘+360∘n,x=−110.03427…∘+360∘n,x=64.37831…∘+360∘n,x=295.62168…∘+360∘n솔루션 단계
2cos(x)+4cos(4x)=0
삼각성을 사용하여 다시 쓰기
2cos(x)+4cos(4x)
cos(4x)=2cos2(2x)−1
cos(4x)
로 고쳐 쓰다=cos(2⋅2x)
더블 앵글 아이덴티티 사용: cos(2x)=2cos2(x)−1cos(2⋅2x)=2cos2(2x)−1=2cos2(2x)−1
=2cos(x)+4(2cos2(2x)−1)
더블 앵글 아이덴티티 사용: cos(2x)=2cos2(x)−1=2cos(x)+4(−1+2(2cos2(x)−1)2)
−1+2(2cos2(x)−1)2확대한다:8cos4(x)−8cos2(x)+1
−1+2(2cos2(x)−1)2
(2cos2(x)−1)2:4cos4(x)−4cos2(x)+1
완벽한 정사각형 공식 적용: (a−b)2=a2−2ab+b2a=2cos2(x),b=1
=(2cos2(x))2−2⋅2cos2(x)⋅1+12
(2cos2(x))2−2⋅2cos2(x)⋅1+12단순화하세요:4cos4(x)−4cos2(x)+1
(2cos2(x))2−2⋅2cos2(x)⋅1+12
규칙 적용 1a=112=1=(2cos2(x))2−2⋅2⋅1⋅cos2(x)+1
(2cos2(x))2=4cos4(x)
(2cos2(x))2
지수 규칙 적용: (a⋅b)n=anbn=22(cos2(x))2
(cos2(x))2:cos4(x)
지수 규칙 적용: (ab)c=abc=cos2⋅2(x)
숫자를 곱하시오: 2⋅2=4=cos4(x)
=22cos4(x)
22=4=4cos4(x)
2⋅2cos2(x)⋅1=4cos2(x)
2⋅2cos2(x)⋅1
숫자를 곱하시오: 2⋅2⋅1=4=4cos2(x)
=4cos4(x)−4cos2(x)+1
=4cos4(x)−4cos2(x)+1
=−1+2(4cos4(x)−4cos2(x)+1)
2(4cos4(x)−4cos2(x)+1)확대한다:8cos4(x)−8cos2(x)+2
2(4cos4(x)−4cos2(x)+1)
괄호 배포=2⋅4cos4(x)+2(−4cos2(x))+2⋅1
마이너스 플러스 규칙 적용+(−a)=−a=2⋅4cos4(x)−2⋅4cos2(x)+2⋅1
2⋅4cos4(x)−2⋅4cos2(x)+2⋅1단순화하세요:8cos4(x)−8cos2(x)+2
2⋅4cos4(x)−2⋅4cos2(x)+2⋅1
숫자를 곱하시오: 2⋅4=8=8cos4(x)−8cos2(x)+2⋅1
숫자를 곱하시오: 2⋅1=2=8cos4(x)−8cos2(x)+2
=8cos4(x)−8cos2(x)+2
=−1+8cos4(x)−8cos2(x)+2
−1+8cos4(x)−8cos2(x)+2단순화하세요:8cos4(x)−8cos2(x)+1
−1+8cos4(x)−8cos2(x)+2
집단적 용어=8cos4(x)−8cos2(x)−1+2
숫자 더하기/ 빼기: −1+2=1=8cos4(x)−8cos2(x)+1
=8cos4(x)−8cos2(x)+1
=2cos(x)+4(8cos4(x)−8cos2(x)+1)
(1−8cos2(x)+8cos4(x))⋅4+2cos(x)=0
대체로 해결
(1−8cos2(x)+8cos4(x))⋅4+2cos(x)=0
하게: cos(x)=u(1−8u2+8u4)⋅4+2u=0
(1−8u2+8u4)⋅4+2u=0:u≈−0.96459…,u≈0.87475…,u≈−0.34258…,u≈0.43242…
(1−8u2+8u4)⋅4+2u=0
(1−8u2+8u4)⋅4+2u 확장 :4−32u2+32u4+2u
(1−8u2+8u4)⋅4+2u
=4(1−8u2+8u4)+2u
4(1−8u2+8u4)확대한다:4−32u2+32u4
4(1−8u2+8u4)
괄호 배포=4⋅1+4(−8u2)+4⋅8u4
마이너스 플러스 규칙 적용+(−a)=−a=4⋅1−4⋅8u2+4⋅8u4
4⋅1−4⋅8u2+4⋅8u4단순화하세요:4−32u2+32u4
4⋅1−4⋅8u2+4⋅8u4
숫자를 곱하시오: 4⋅1=4=4−4⋅8u2+4⋅8u4
숫자를 곱하시오: 4⋅8=32=4−32u2+32u4
=4−32u2+32u4
=4−32u2+32u4+2u
4−32u2+32u4+2u=0
표준 양식으로 작성 anxn+…+a1x+a0=032u4−32u2+2u+4=0
다음을 위한 하나의 솔루션 찾기 32u4−32u2+2u+4=0 뉴턴-랩슨을 이용하여:u≈−0.96459…
32u4−32u2+2u+4=0
뉴턴-랩슨 근사 정의
f(u)=32u4−32u2+2u+4
f′(u)찾다 :128u3−64u+2
dud(32u4−32u2+2u+4)
합계/차이 규칙 적용: (f±g)′=f′±g′=dud(32u4)−dud(32u2)+dud(2u)+dud(4)
dud(32u4)=128u3
dud(32u4)
정수를 빼라: (a⋅f)′=a⋅f′=32dud(u4)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=32⋅4u4−1
단순화=128u3
dud(32u2)=64u
dud(32u2)
정수를 빼라: (a⋅f)′=a⋅f′=32dud(u2)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=32⋅2u2−1
단순화=64u
dud(2u)=2
dud(2u)
정수를 빼라: (a⋅f)′=a⋅f′=2dudu
공통 도함수 적용: dudu=1=2⋅1
단순화=2
dud(4)=0
dud(4)
상수의 도함수: dxd(a)=0=0
=128u3−64u+2+0
단순화=128u3−64u+2
렛 u0=−2계산하다 un+1 까지 Δun+1<0.000001
u1=−1.57046…:Δu1=0.42953…
f(u0)=32(−2)4−32(−2)2+2(−2)+4=384f′(u0)=128(−2)3−64(−2)+2=−894u1=−1.57046…
Δu1=∣−1.57046…−(−2)∣=0.42953…Δu1=0.42953…
u2=−1.27401…:Δu2=0.29645…
f(u1)=32(−1.57046…)4−32(−1.57046…)2+2(−1.57046…)+4=116.59128…f′(u1)=128(−1.57046…)3−64(−1.57046…)+2=−393.28104…u2=−1.27401…
Δu2=∣−1.27401…−(−1.57046…)∣=0.29645…Δu2=0.29645…
u3=−1.08733…:Δu3=0.18667…
f(u2)=32(−1.27401…)4−32(−1.27401…)2+2(−1.27401…)+4=33.81573…f′(u2)=128(−1.27401…)3−64(−1.27401…)+2=−181.14887…u3=−1.08733…
Δu3=∣−1.08733…−(−1.27401…)∣=0.18667…Δu3=0.18667…
u4=−0.99350…:Δu4=0.09382…
f(u3)=32(−1.08733…)4−32(−1.08733…)2+2(−1.08733…)+4=8.72257…f′(u3)=128(−1.08733…)3−64(−1.08733…)+2=−92.96260…u4=−0.99350…
Δu4=∣−0.99350…−(−1.08733…)∣=0.09382…Δu4=0.09382…
u5=−0.96674…:Δu5=0.02676…
f(u4)=32(−0.99350…)4−32(−0.99350…)2+2(−0.99350…)+4=1.60428…f′(u4)=128(−0.99350…)3−64(−0.99350…)+2=−59.93911…u5=−0.96674…
Δu5=∣−0.96674…−(−0.99350…)∣=0.02676…Δu5=0.02676…
u6=−0.96461…:Δu6=0.00213…
f(u5)=32(−0.96674…)4−32(−0.96674…)2+2(−0.96674…)+4=0.11041…f′(u5)=128(−0.96674…)3−64(−0.96674…)+2=−51.77809…u6=−0.96461…
Δu6=∣−0.96461…−(−0.96674…)∣=0.00213…Δu6=0.00213…
u7=−0.96459…:Δu7=0.00001…
f(u6)=32(−0.96461…)4−32(−0.96461…)2+2(−0.96461…)+4=0.00066…f′(u6)=128(−0.96461…)3−64(−0.96461…)+2=−51.15092…u7=−0.96459…
Δu7=∣−0.96459…−(−0.96461…)∣=0.00001…Δu7=0.00001…
u8=−0.96459…:Δu8=4.90935E−10
f(u7)=32(−0.96459…)4−32(−0.96459…)2+2(−0.96459…)+4=2.51099E−8f′(u7)=128(−0.96459…)3−64(−0.96459…)+2=−51.14709…u8=−0.96459…
Δu8=∣−0.96459…−(−0.96459…)∣=4.90935E−10Δu8=4.90935E−10
u≈−0.96459…
긴 나눗셈 적용:u+0.96459…32u4−32u2+2u+4=32u3−30.86715…u2−2.22559…u+4.14680…
32u3−30.86715…u2−2.22559…u+4.14680…≈0
다음을 위한 하나의 솔루션 찾기 32u3−30.86715…u2−2.22559…u+4.14680…=0 뉴턴-랩슨을 이용하여:u≈0.87475…
32u3−30.86715…u2−2.22559…u+4.14680…=0
뉴턴-랩슨 근사 정의
f(u)=32u3−30.86715…u2−2.22559…u+4.14680…
f′(u)찾다 :96u2−61.73430…u−2.22559…
dud(32u3−30.86715…u2−2.22559…u+4.14680…)
합계/차이 규칙 적용: (f±g)′=f′±g′=dud(32u3)−dud(30.86715…u2)−dud(2.22559…u)+dud(4.14680…)
dud(32u3)=96u2
dud(32u3)
정수를 빼라: (a⋅f)′=a⋅f′=32dud(u3)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=32⋅3u3−1
단순화=96u2
dud(30.86715…u2)=61.73430…u
dud(30.86715…u2)
정수를 빼라: (a⋅f)′=a⋅f′=30.86715…dud(u2)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=30.86715…⋅2u2−1
단순화=61.73430…u
dud(2.22559…u)=2.22559…
dud(2.22559…u)
정수를 빼라: (a⋅f)′=a⋅f′=2.22559…dudu
공통 도함수 적용: dudu=1=2.22559…⋅1
단순화=2.22559…
dud(4.14680…)=0
dud(4.14680…)
상수의 도함수: dxd(a)=0=0
=96u2−61.73430…u−2.22559…+0
단순화=96u2−61.73430…u−2.22559…
렛 u0=2계산하다 un+1 까지 Δun+1<0.000001
u1=1.48809…:Δu1=0.51190…
f(u0)=32⋅23−30.86715…⋅22−2.22559…⋅2+4.14680…=132.22701…f′(u0)=96⋅22−61.73430…⋅2−2.22559…=258.30580…u1=1.48809…
Δu1=∣1.48809…−2∣=0.51190…Δu1=0.51190…
u2=1.16798…:Δu2=0.32011…
f(u1)=32⋅1.48809…3−30.86715…⋅1.48809…2−2.22559…⋅1.48809…+4.14680…=37.93120…f′(u1)=96⋅1.48809…2−61.73430…⋅1.48809…−2.22559…=118.49374…u2=1.16798…
Δu2=∣1.16798…−1.48809…∣=0.32011…Δu2=0.32011…
u3=0.98388…:Δu3=0.18410…
f(u2)=32⋅1.16798…3−30.86715…⋅1.16798…2−2.22559…⋅1.16798…+4.14680…=10.42612…f′(u2)=96⋅1.16798…2−61.73430…⋅1.16798…−2.22559…=56.63221…u3=0.98388…
Δu3=∣0.98388…−1.16798…∣=0.18410…Δu3=0.18410…
u4=0.89863…:Δu4=0.08524…
f(u3)=32⋅0.98388…3−30.86715…⋅0.98388…2−2.22559…⋅0.98388…+4.14680…=2.55451…f′(u3)=96⋅0.98388…2−61.73430…⋅0.98388…−2.22559…=29.96580…u4=0.89863…
Δu4=∣0.89863…−0.98388…∣=0.08524…Δu4=0.08524…
u5=0.87632…:Δu5=0.02231…
f(u4)=32⋅0.89863…3−30.86715…⋅0.89863…2−2.22559…⋅0.89863…+4.14680…=0.44226…f′(u4)=96⋅0.89863…2−61.73430…⋅0.89863…−2.22559…=19.82237…u5=0.87632…
Δu5=∣0.87632…−0.89863…∣=0.02231…Δu5=0.02231…
u6=0.87476…:Δu6=0.00156…
f(u5)=32⋅0.87632…3−30.86715…⋅0.87632…2−2.22559…⋅0.87632…+4.14680…=0.02722…f′(u5)=96⋅0.87632…2−61.73430…⋅0.87632…−2.22559…=17.39797…u6=0.87476…
Δu6=∣0.87476…−0.87632…∣=0.00156…Δu6=0.00156…
u7=0.87475…:Δu7=7.56069E−6
f(u6)=32⋅0.87476…3−30.86715…⋅0.87476…2−2.22559…⋅0.87476…+4.14680…=0.00013…f′(u6)=96⋅0.87476…2−61.73430…⋅0.87476…−2.22559…=17.23152…u7=0.87475…
Δu7=∣0.87475…−0.87476…∣=7.56069E−6Δu7=7.56069E−6
u8=0.87475…:Δu8=1.76195E−10
f(u7)=32⋅0.87475…3−30.86715…⋅0.87475…2−2.22559…⋅0.87475…+4.14680…=3.03597E−9f′(u7)=96⋅0.87475…2−61.73430…⋅0.87475…−2.22559…=17.23072…u8=0.87475…
Δu8=∣0.87475…−0.87475…∣=1.76195E−10Δu8=1.76195E−10
u≈0.87475…
긴 나눗셈 적용:u−0.87475…32u3−30.86715…u2−2.22559…u+4.14680…=32u2−2.87503…u−4.74053…
32u2−2.87503…u−4.74053…≈0
다음을 위한 하나의 솔루션 찾기 32u2−2.87503…u−4.74053…=0 뉴턴-랩슨을 이용하여:u≈−0.34258…
32u2−2.87503…u−4.74053…=0
뉴턴-랩슨 근사 정의
f(u)=32u2−2.87503…u−4.74053…
f′(u)찾다 :64u−2.87503…
dud(32u2−2.87503…u−4.74053…)
합계/차이 규칙 적용: (f±g)′=f′±g′=dud(32u2)−dud(2.87503…u)−dud(4.74053…)
dud(32u2)=64u
dud(32u2)
정수를 빼라: (a⋅f)′=a⋅f′=32dud(u2)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=32⋅2u2−1
단순화=64u
dud(2.87503…u)=2.87503…
dud(2.87503…u)
정수를 빼라: (a⋅f)′=a⋅f′=2.87503…dudu
공통 도함수 적용: dudu=1=2.87503…⋅1
단순화=2.87503…
dud(4.74053…)=0
dud(4.74053…)
상수의 도함수: dxd(a)=0=0
=64u−2.87503…−0
단순화=64u−2.87503…
렛 u0=−2계산하다 un+1 까지 Δun+1<0.000001
u1=−1.01425…:Δu1=0.98574…
f(u0)=32(−2)2−2.87503…(−2)−4.74053…=129.00952…f′(u0)=64(−2)−2.87503…=−130.87503…u1=−1.01425…
Δu1=∣−1.01425…−(−2)∣=0.98574…Δu1=0.98574…
u2=−0.55555…:Δu2=0.45870…
f(u1)=32(−1.01425…)2−2.87503…(−1.01425…)−4.74053…=31.09423…f′(u1)=64(−1.01425…)−2.87503…=−67.78729…u2=−0.55555…
Δu2=∣−0.55555…−(−1.01425…)∣=0.45870…Δu2=0.45870…
u3=−0.38034…:Δu3=0.17520…
f(u2)=32(−0.55555…)2−2.87503…(−0.55555…)−4.74053…=6.73307…f′(u2)=64(−0.55555…)−2.87503…=−38.43029…u3=−0.38034…
Δu3=∣−0.38034…−(−0.55555…)∣=0.17520…Δu3=0.17520…
u4=−0.34425…:Δu4=0.03608…
f(u3)=32(−0.38034…)2−2.87503…(−0.38034…)−4.74053…=0.98226…f′(u3)=64(−0.38034…)−2.87503…=−27.21735…u4=−0.34425…
Δu4=∣−0.34425…−(−0.38034…)∣=0.03608…Δu4=0.03608…
u5=−0.34258…:Δu5=0.00167…
f(u4)=32(−0.34425…)2−2.87503…(−0.34425…)−4.74053…=0.04167…f′(u4)=64(−0.34425…)−2.87503…=−24.90762…u5=−0.34258…
Δu5=∣−0.34258…−(−0.34425…)∣=0.00167…Δu5=0.00167…
u6=−0.34258…:Δu6=3.6129E−6
f(u5)=32(−0.34258…)2−2.87503…(−0.34258…)−4.74053…=0.00008…f′(u5)=64(−0.34258…)−2.87503…=−24.80052…u6=−0.34258…
Δu6=∣−0.34258…−(−0.34258…)∣=3.6129E−6Δu6=3.6129E−6
u7=−0.34258…:Δu7=1.68425E−11
f(u6)=32(−0.34258…)2−2.87503…(−0.34258…)−4.74053…=4.17699E−10f′(u6)=64(−0.34258…)−2.87503…=−24.80029…u7=−0.34258…
Δu7=∣−0.34258…−(−0.34258…)∣=1.68425E−11Δu7=1.68425E−11
u≈−0.34258…
긴 나눗셈 적용:u+0.34258…32u2−2.87503…u−4.74053…=32u−13.83766…
32u−13.83766…≈0
u≈0.43242…
해결책은u≈−0.96459…,u≈0.87475…,u≈−0.34258…,u≈0.43242…
뒤로 대체 u=cos(x)cos(x)≈−0.96459…,cos(x)≈0.87475…,cos(x)≈−0.34258…,cos(x)≈0.43242…
cos(x)≈−0.96459…,cos(x)≈0.87475…,cos(x)≈−0.34258…,cos(x)≈0.43242…
cos(x)=−0.96459…:x=arccos(−0.96459…)+2πn,x=−arccos(−0.96459…)+2πn
cos(x)=−0.96459…
트리거 역속성 적용
cos(x)=−0.96459…
일반 솔루션 cos(x)=−0.96459…cos(x)=−a⇒x=arccos(−a)+2πn,x=−arccos(−a)+2πnx=arccos(−0.96459…)+2πn,x=−arccos(−0.96459…)+2πn
x=arccos(−0.96459…)+2πn,x=−arccos(−0.96459…)+2πn
cos(x)=0.87475…:x=arccos(0.87475…)+2πn,x=2π−arccos(0.87475…)+2πn
cos(x)=0.87475…
트리거 역속성 적용
cos(x)=0.87475…
일반 솔루션 cos(x)=0.87475…cos(x)=a⇒x=arccos(a)+2πn,x=2π−arccos(a)+2πnx=arccos(0.87475…)+2πn,x=2π−arccos(0.87475…)+2πn
x=arccos(0.87475…)+2πn,x=2π−arccos(0.87475…)+2πn
cos(x)=−0.34258…:x=arccos(−0.34258…)+2πn,x=−arccos(−0.34258…)+2πn
cos(x)=−0.34258…
트리거 역속성 적용
cos(x)=−0.34258…
일반 솔루션 cos(x)=−0.34258…cos(x)=−a⇒x=arccos(−a)+2πn,x=−arccos(−a)+2πnx=arccos(−0.34258…)+2πn,x=−arccos(−0.34258…)+2πn
x=arccos(−0.34258…)+2πn,x=−arccos(−0.34258…)+2πn
cos(x)=0.43242…:x=arccos(0.43242…)+2πn,x=2π−arccos(0.43242…)+2πn
cos(x)=0.43242…
트리거 역속성 적용
cos(x)=0.43242…
일반 솔루션 cos(x)=0.43242…cos(x)=a⇒x=arccos(a)+2πn,x=2π−arccos(a)+2πnx=arccos(0.43242…)+2πn,x=2π−arccos(0.43242…)+2πn
x=arccos(0.43242…)+2πn,x=2π−arccos(0.43242…)+2πn
모든 솔루션 결합x=arccos(−0.96459…)+2πn,x=−arccos(−0.96459…)+2πn,x=arccos(0.87475…)+2πn,x=2π−arccos(0.87475…)+2πn,x=arccos(−0.34258…)+2πn,x=−arccos(−0.34258…)+2πn,x=arccos(0.43242…)+2πn,x=2π−arccos(0.43242…)+2πn
해를 10진수 형식으로 표시x=2.87471…+2πn,x=−2.87471…+2πn,x=0.50586…+2πn,x=2π−0.50586…+2πn,x=1.92046…+2πn,x=−1.92046…+2πn,x=1.12361…+2πn,x=2π−1.12361…+2πn