해법
cos(x)+cos4(x)=21
해법
x=1.09667…+2πn,x=2π−1.09667…+2πn
+1
도
x=62.83512…∘+360∘n,x=297.16487…∘+360∘n솔루션 단계
cos(x)+cos4(x)=21
대체로 해결
cos(x)+cos4(x)=21
하게: cos(x)=uu+u4=21
u+u4=21:u≈0.45655…,u≈−1.12990…
u+u4=21
양쪽을 곱한 값 2
u+u4=21
양쪽을 곱한 값 2u⋅2+u4⋅2=21⋅2
단순화2u+2u4=1
2u+2u4=1
1를 왼쪽으로 이동
2u+2u4=1
빼다 1 양쪽에서2u+2u4−1=1−1
단순화2u+2u4−1=0
2u+2u4−1=0
표준 양식으로 작성 anxn+…+a1x+a0=02u4+2u−1=0
다음을 위한 하나의 솔루션 찾기 2u4+2u−1=0 뉴턴-랩슨을 이용하여:u≈0.45655…
2u4+2u−1=0
뉴턴-랩슨 근사 정의
f(u)=2u4+2u−1
f′(u)찾다 :8u3+2
dud(2u4+2u−1)
합계/차이 규칙 적용: (f±g)′=f′±g′=dud(2u4)+dud(2u)−dud(1)
dud(2u4)=8u3
dud(2u4)
정수를 빼라: (a⋅f)′=a⋅f′=2dud(u4)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=2⋅4u4−1
단순화=8u3
dud(2u)=2
dud(2u)
정수를 빼라: (a⋅f)′=a⋅f′=2dudu
공통 도함수 적용: dudu=1=2⋅1
단순화=2
dud(1)=0
dud(1)
상수의 도함수: dxd(a)=0=0
=8u3+2−0
단순화=8u3+2
렛 u0=1계산하다 un+1 까지 Δun+1<0.000001
u1=0.7:Δu1=0.3
f(u0)=2⋅14+2⋅1−1=3f′(u0)=8⋅13+2=10u1=0.7
Δu1=∣0.7−1∣=0.3Δu1=0.3
u2=0.51446…:Δu2=0.18553…
f(u1)=2⋅0.74+2⋅0.7−1=0.8802f′(u1)=8⋅0.73+2=4.744u2=0.51446…
Δu2=∣0.51446…−0.7∣=0.18553…Δu2=0.18553…
u3=0.45974…:Δu3=0.05471…
f(u2)=2⋅0.51446…4+2⋅0.51446…−1=0.16902…f′(u2)=8⋅0.51446…3+2=3.08929…u3=0.45974…
Δu3=∣0.45974…−0.51446…∣=0.05471…Δu3=0.05471…
u4=0.45656…:Δu4=0.00318…
f(u3)=2⋅0.45974…4+2⋅0.45974…−1=0.00885…f′(u3)=8⋅0.45974…3+2=2.77741…u4=0.45656…
Δu4=∣0.45656…−0.45974…∣=0.00318…Δu4=0.00318…
u5=0.45655…:Δu5=9.28514E−6
f(u4)=2⋅0.45656…4+2⋅0.45656…−1=0.00002…f′(u4)=8⋅0.45656…3+2=2.76135…u5=0.45655…
Δu5=∣0.45655…−0.45656…∣=9.28514E−6Δu5=9.28514E−6
u6=0.45655…:Δu6=7.80973E−11
f(u5)=2⋅0.45655…4+2⋅0.45655…−1=2.15651E−10f′(u5)=8⋅0.45655…3+2=2.76131…u6=0.45655…
Δu6=∣0.45655…−0.45655…∣=7.80973E−11Δu6=7.80973E−11
u≈0.45655…
긴 나눗셈 적용:u−0.45655…2u4+2u−1=2u3+0.91310…u2+0.41688…u+2.19032…
2u3+0.91310…u2+0.41688…u+2.19032…≈0
다음을 위한 하나의 솔루션 찾기 2u3+0.91310…u2+0.41688…u+2.19032…=0 뉴턴-랩슨을 이용하여:u≈−1.12990…
2u3+0.91310…u2+0.41688…u+2.19032…=0
뉴턴-랩슨 근사 정의
f(u)=2u3+0.91310…u2+0.41688…u+2.19032…
f′(u)찾다 :6u2+1.82621…u+0.41688…
dud(2u3+0.91310…u2+0.41688…u+2.19032…)
합계/차이 규칙 적용: (f±g)′=f′±g′=dud(2u3)+dud(0.91310…u2)+dud(0.41688…u)+dud(2.19032…)
dud(2u3)=6u2
dud(2u3)
정수를 빼라: (a⋅f)′=a⋅f′=2dud(u3)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=2⋅3u3−1
단순화=6u2
dud(0.91310…u2)=1.82621…u
dud(0.91310…u2)
정수를 빼라: (a⋅f)′=a⋅f′=0.91310…dud(u2)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=0.91310…⋅2u2−1
단순화=1.82621…u
dud(0.41688…u)=0.41688…
dud(0.41688…u)
정수를 빼라: (a⋅f)′=a⋅f′=0.41688…dudu
공통 도함수 적용: dudu=1=0.41688…⋅1
단순화=0.41688…
dud(2.19032…)=0
dud(2.19032…)
상수의 도함수: dxd(a)=0=0
=6u2+1.82621…u+0.41688…+0
단순화=6u2+1.82621…u+0.41688…
렛 u0=−5계산하다 un+1 까지 Δun+1<0.000001
u1=−3.39285…:Δu1=1.60714…
f(u0)=2(−5)3+0.91310…(−5)2+0.41688…(−5)+2.19032…=−227.06644…f′(u0)=6(−5)2+1.82621…(−5)+0.41688…=141.28582…u1=−3.39285…
Δu1=∣−3.39285…−(−5)∣=1.60714…Δu1=1.60714…
u2=−2.33697…:Δu2=1.05588…
f(u1)=2(−3.39285…)3+0.91310…(−3.39285…)2+0.41688…(−3.39285…)+2.19032…=−66.82653…f′(u1)=6(−3.39285…)2+1.82621…(−3.39285…)+0.41688…=63.28970…u2=−2.33697…
Δu2=∣−2.33697…−(−3.39285…)∣=1.05588…Δu2=1.05588…
u3=−1.66874…:Δu3=0.66822…
f(u2)=2(−2.33697…)3+0.91310…(−2.33697…)2+0.41688…(−2.33697…)+2.19032…=−19.32356…f′(u2)=6(−2.33697…)2+1.82621…(−2.33697…)+0.41688…=28.91776…u3=−1.66874…
Δu3=∣−1.66874…−(−2.33697…)∣=0.66822…Δu3=0.66822…
u4=−1.29535…:Δu4=0.37339…
f(u3)=2(−1.66874…)3+0.91310…(−1.66874…)2+0.41688…(−1.66874…)+2.19032…=−5.25661…f′(u3)=6(−1.66874…)2+1.82621…(−1.66874…)+0.41688…=14.07774…u4=−1.29535…
Δu4=∣−1.29535…−(−1.66874…)∣=0.37339…Δu4=0.37339…
u5=−1.15191…:Δu5=0.14343…
f(u4)=2(−1.29535…)3+0.91310…(−1.29535…)2+0.41688…(−1.29535…)+2.19032…=−1.16457…f′(u4)=6(−1.29535…)2+1.82621…(−1.29535…)+0.41688…=8.11890…u5=−1.15191…
Δu5=∣−1.15191…−(−1.29535…)∣=0.14343…Δu5=0.14343…
u6=−1.13036…:Δu6=0.02155…
f(u5)=2(−1.15191…)3+0.91310…(−1.15191…)2+0.41688…(−1.15191…)+2.19032…=−0.13522…f′(u5)=6(−1.15191…)2+1.82621…(−1.15191…)+0.41688…=6.27464…u6=−1.13036…
Δu6=∣−1.13036…−(−1.15191…)∣=0.02155…Δu6=0.02155…
u7=−1.12990…:Δu7=0.00045…
f(u6)=2(−1.13036…)3+0.91310…(−1.13036…)2+0.41688…(−1.13036…)+2.19032…=−0.00276…f′(u6)=6(−1.13036…)2+1.82621…(−1.13036…)+0.41688…=6.01889…u7=−1.12990…
Δu7=∣−1.12990…−(−1.13036…)∣=0.00045…Δu7=0.00045…
u8=−1.12990…:Δu8=2.06048E−7
f(u7)=2(−1.12990…)3+0.91310…(−1.12990…)2+0.41688…(−1.12990…)+2.19032…=−1.23907E−6f′(u7)=6(−1.12990…)2+1.82621…(−1.12990…)+0.41688…=6.01350…u8=−1.12990…
Δu8=∣−1.12990…−(−1.12990…)∣=2.06048E−7Δu8=2.06048E−7
u≈−1.12990…
긴 나눗셈 적용:u+1.12990…2u3+0.91310…u2+0.41688…u+2.19032…=2u2−1.34669…u+1.93851…
2u2−1.34669…u+1.93851…≈0
다음을 위한 하나의 솔루션 찾기 2u2−1.34669…u+1.93851…=0 뉴턴-랩슨을 이용하여:솔루션 없음 u∈R
2u2−1.34669…u+1.93851…=0
뉴턴-랩슨 근사 정의
f(u)=2u2−1.34669…u+1.93851…
f′(u)찾다 :4u−1.34669…
dud(2u2−1.34669…u+1.93851…)
합계/차이 규칙 적용: (f±g)′=f′±g′=dud(2u2)−dud(1.34669…u)+dud(1.93851…)
dud(2u2)=4u
dud(2u2)
정수를 빼라: (a⋅f)′=a⋅f′=2dud(u2)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=2⋅2u2−1
단순화=4u
dud(1.34669…u)=1.34669…
dud(1.34669…u)
정수를 빼라: (a⋅f)′=a⋅f′=1.34669…dudu
공통 도함수 적용: dudu=1=1.34669…⋅1
단순화=1.34669…
dud(1.93851…)=0
dud(1.93851…)
상수의 도함수: dxd(a)=0=0
=4u−1.34669…+0
단순화=4u−1.34669…
렛 u0=1계산하다 un+1 까지 Δun+1<0.000001
u1=0.02317…:Δu1=0.97682…
f(u0)=2⋅12−1.34669…⋅1+1.93851…=2.59181…f′(u0)=4⋅1−1.34669…=2.65330…u1=0.02317…
Δu1=∣0.02317…−1∣=0.97682…Δu1=0.97682…
u2=1.54500…:Δu2=1.52183…
f(u1)=2⋅0.02317…2−1.34669…⋅0.02317…+1.93851…=1.90837…f′(u1)=4⋅0.02317…−1.34669…=−1.25400…u2=1.54500…
Δu2=∣1.54500…−0.02317…∣=1.52183…Δu2=1.52183…
u3=0.58667…:Δu3=0.95833…
f(u2)=2⋅1.54500…2−1.34669…⋅1.54500…+1.93851…=4.63194…f′(u2)=4⋅1.54500…−1.34669…=4.83332…u3=0.58667…
Δu3=∣0.58667…−1.54500…∣=0.95833…Δu3=0.95833…
u4=−1.25016…:Δu4=1.83683…
f(u3)=2⋅0.58667…2−1.34669…⋅0.58667…+1.93851…=1.83681…f′(u3)=4⋅0.58667…−1.34669…=0.99998…u4=−1.25016…
Δu4=∣−1.25016…−0.58667…∣=1.83683…Δu4=1.83683…
u5=−0.18705…:Δu5=1.06311…
f(u4)=2(−1.25016…)2−1.34669…(−1.25016…)+1.93851…=6.74795…f′(u4)=4(−1.25016…)−1.34669…=−6.34736…u5=−0.18705…
Δu5=∣−0.18705…−(−1.25016…)∣=1.06311…Δu5=1.06311…
u6=0.89193…:Δu6=1.07898…
f(u5)=2(−0.18705…)2−1.34669…(−0.18705…)+1.93851…=2.26040…f′(u5)=4(−0.18705…)−1.34669…=−2.09492…u6=0.89193…
Δu6=∣0.89193…−(−0.18705…)∣=1.07898…Δu6=1.07898…
u7=−0.15642…:Δu7=1.04835…
f(u6)=2⋅0.89193…2−1.34669…⋅0.89193…+1.93851…=2.32843…f′(u6)=4⋅0.89193…−1.34669…=2.22102…u7=−0.15642…
Δu7=∣−0.15642…−0.89193…∣=1.04835…Δu7=1.04835…
u8=0.95800…:Δu8=1.11443…
f(u7)=2(−0.15642…)2−1.34669…(−0.15642…)+1.93851…=2.19811…f′(u7)=4(−0.15642…)−1.34669…=−1.97241…u8=0.95800…
Δu8=∣0.95800…−(−0.15642…)∣=1.11443…Δu8=1.11443…
해결 방법을 찾을 수 없습니다
해결책은u≈0.45655…,u≈−1.12990…
뒤로 대체 u=cos(x)cos(x)≈0.45655…,cos(x)≈−1.12990…
cos(x)≈0.45655…,cos(x)≈−1.12990…
cos(x)=0.45655…:x=arccos(0.45655…)+2πn,x=2π−arccos(0.45655…)+2πn
cos(x)=0.45655…
트리거 역속성 적용
cos(x)=0.45655…
일반 솔루션 cos(x)=0.45655…cos(x)=a⇒x=arccos(a)+2πn,x=2π−arccos(a)+2πnx=arccos(0.45655…)+2πn,x=2π−arccos(0.45655…)+2πn
x=arccos(0.45655…)+2πn,x=2π−arccos(0.45655…)+2πn
cos(x)=−1.12990…:해결책 없음
cos(x)=−1.12990…
−1≤cos(x)≤1해결책없음
모든 솔루션 결합x=arccos(0.45655…)+2πn,x=2π−arccos(0.45655…)+2πn
해를 10진수 형식으로 표시x=1.09667…+2πn,x=2π−1.09667…+2πn